At Diagnosis

7/21/2019 At Diagnosis

1/501

2003 AUTOMATIC TRANSMISSIONS

Al lison LCT 1000 Diagnosis

APPLICATION

TRANSMISSION APPLICATION

IDENTIFICATION

TRANSMISSION

Transmission is identified by metal identification plate attached to right side of transmission case. See Fig. 1 .

WARNING: Vehicle is equipped with Supplemental Inflatable Restraint (SIR) system.When servic ing vehicle, use care to avoid accidental air bag deployment.SIR system-related components are located in various locationsthroughout interior and exterior of vehicle, depending on application. Donot use electrical test equipment on or near these circui ts. If necessary,deactivate SIR system before servicing components. See AIR BAGDEACTIVATION PROCEDURES article in GENERAL INFORMATION.

ApplicationTransmission Model

(RPO)

Chevrolet Cab & Chassis Silverado 3500, Silverado 2500 HD & Silverado3500 (6.6L & 8.1L)

LCT 1000 (M74)

GMC Cab & Chassis Sierra 3500, Sierra 2500 HD & Sierra 3500 (6.6L &8.1L)

LCT 1000 (M74)


2/501

Fig. 1: Locating Transmission Identification PlateCourtesy of GENERAL MOTORS CORP.

DESCRIPTION & OPERATION

INTRODUCTION

Allison 1000 series transmissions are torque converter driven, fully automatic, transmission systems. The 1000series transmissions have up to five forward speeds, Neutral, and Reverse. The 5th gear is an overdrive gearratio. The 1000 series incorporates a variety of standard and optional design features. These design features are:

Direct mount to engine block.

Flexplate drive.

Torque Converter with a Torque Converter Clutch (TCC) and integral vibration damper. Three constant-mesh, planetary gear sets with helical gears.

Five multiple disk clutches, two rotating and three stationary.

Common hydraulic system for all transmission functions.

Two transmission fluid filtration systems.

Electro-hydraulic control valve assembly.

Electronically controlled automatic gear selection and clutch apply.


3/501

Provision for remote transmission fluid cooler.

Fill tube/dipstick provision on both sides of transmission.

Parking pawl.

Power Take Off (PTO) provision on both sides of transmission.

Variety of available output yokes or flanges.

TRANSMISSION COMPONENTS & SYSTEMS

Torque Converter

Several torque converters are available to match the transmissions to a wide variety of diesel and gasolineengines. The torque converter is a single-stage, polyphase, and three-element unit, consisting of a pump, stator,and turbine. At lower output speeds, the torque converter multiplies torque and provides a fluid coupling to the

engine. At higher speeds, the Torque Converter Clutch (TCC) is automatically engaged to provide direct drivefrom the engine to the transmission. Hydraulic fluid for converter charging pressure comes from the sump andis supplied by the input pump. The torque converter clutch is applied or released by changing direction of fluidin the torque converter. An integral converter damper minimizes the need for additional engine vibrationcontrol.

Gear Sets

The planetary gear train includes three constant-mesh planetary gear sets containing helical gears. By theengagement of the clutches in various combinations, the planetary sets act independently or together to providefive forward gear ranges, Neutral, and Reverse.

Clutches

Five clutches (two rotating and three stationary) direct the flow of torque through the transmission. All rangeclutches are hydraulically actuated and spring-released, with automatic wear compensation. The transmission

fluid cools the clutches. The Transmission Control Module (TCM) signals solenoid valves to apply and releaseclutches based on speed and power combinations and the gear range selected by the operator.

Hydraulic System

A common hydraulic system serves the torque converter and the transmission. Transmission fluid for allhydraulic operations, lubrication, and cooling comes from the sump and is supplied by the charging pump.

Transmission Fluid Filtration

Fluid filtration is provided by two filter systems. A suction filter, located in the sump, provides generalprotection to the entire hydraulic system by filtering large particulates. A spin-on filter provides full-timeprotection for the control solenoids and multipass protection for the entire system. The spin-on filter isexternally located on the converter housing at the lower left front of the transmission.

Electro-Hydraulic Control Valve Assembly


4/501

The control valve assembly consists of two components. The main valve body contains the trim valves, theTCC valve, the exhaust backfill valve, and the control main relief valve. The shift valve body contains the shiftvalves, the control main pressure valve, and the manual selector valve. The control valve assembly attaches tothe bottom of the transmission and is enclosed by the oil pan.

Remote Oil Cooler Provision

Ports for remote-mount oil cooler lines are located on the right side of the converter housing near the converterhousing/main housing splitline. Remote oil-to-water coolers require plumbing for transmission fluid andengine-cooling water. Remote oil-to-air coolers may also be used, and only transmission fluid lines need to beprovided. Heat is transferred from the transmission fluid to either water or air depending upon the cooler typeused.

Fill Tube/Dipstick Provision

All 1000 series transmissions have a fill tube/dipstick provision on both sides of the transmission. The fill tubeand dipstick are installed and adapted as specified by the vehicle manufacturer. A plug is installed in the unusedlocation.

Park Pawl

All 1000 series transmissions have a parking pawl. The internal parking pawl is engaged by selection of Park onthe gearshift lever.

PTO Provision

The 1000 series transmissions have a provision to mount and drive a PTO unit on the left and/or right side ofthe transmission housing. The torque converter turbine drives the optional PTO drive gear. The PTO reflectsengine and torque converter characteristics. The vehicle manufacturer and/or body builder provides PTO unitsand associated controls.

Output Yoke/Flange

A variety of output yokes or flanges are available to meet vehicle driveline requirements. Yokes or flanges areinstalled and are adapted as specified by the vehicle manufacturer.

ADAPT FUNCTION

The Transmission Control Module (TCM) produces excellent shift quality by applying closed loop control that

NOTE: When replacing a failed transmission with a replacement unit, i t is important toreset the TCM to base calibration and fast adaptive for all shifts . This can bedone in one step with the scan tool . If this is not done, the TCM's adaptivevalues will sti ll be at the settings that it learned for the old transmission, andwill be in slow adaptive mode. Under these condit ions, it would take anunacceptably long time for the adaptive values to converge to levels sui table forthe new transmission.


5/501


6/501

slow adaptive, and thus it is not unusual to experience somewhat harsh or unpleasant shift quality until theseshifts are adapted.

TCC engagement is accomplished by a separate Pulse Width Modulated (PWM) solenoid labeled "F" in thetransmission. There are adaptive values for this as well, and thus it will also require some driving for TCCengagement to converge.

If you are experiencing harsh shifts, it is important to verify whether the particular shift is converged. Use thescan tool to determine if the problem shift is converged.

If it is not, the TCM is still learning how to adapt that shift, and simply needs to be driven a bit more withthe intention of performing more of the particular type of shift.

If a particular shift is converged, but still objectionable, it's good trouble shooting practice to reset theadaptive values for that shift back to base calibration level. This will automatically reset the TCM to fast

adaptive mode. The vehicle should then be driven to allow the TCM to re-learn the shift. Many times thiswill correct the problem. It is possible to reset individual shifts without affecting the other shifts.

TRANSMISSION INDICATORS & MESSAGES

Normal Inhibits Which Result In Blinking PRNDL

Inhibits which result in a blinking PRNDL are as follows:

High engine speed Neutral to gear range shifts when a Neutral to Drive or Neutral to Reverse shift ismade when engine RPM is too high, the shift will be inhibited to Neutral. The TCM has torquemanagement capability and will attempt to slow the engine to a point where it will make the requestedshift.

High throttle or torque direction change shifts from Reverse to Drive, Drive to Reverse, Neutral to Drive,and Neutral to Reverse shifts where throttle position is greater then 25 percent transmission will beinhibited to Neutral. The TCM has torque management capability, and will attempt to slow the engine to

a point where it will make the requested shift. If the 4-wheel drive transfer case is shifted into Neutral while the transmission is in Drive or Reverse, the

transmission will continue to command the gear range until output speed is low, at which point Neutral iscommanded. If the driver attempts to shift the transmission from Neutral to Drive or Neutral to Reversewith the transfer case in Neutral, the PRNDL display will blink immediately.

High output speed direction change shifts Reverse to Drive, Drive to Reverse, and Neutral to Reverseshifts initiated above 300 RPM output speed will be inhibited to Neutral.

Insufficient transmission fluid and lack of initial pump prime caused by refilling the transmission. Extremely low transmission fluid temperature. A shift out of Neutral when ATF temperature is below -

49F (-45C) may be inhibited.

Blinking PRNDL

Malfunctions which may cause a blinking PRNDL are as follows:

Failure to detect turbine s eed ull down durin a shift This ma occur for exam le when a clutch is


7/501

failed and the transmission cannot attain the requested range.

Invalid gear ratio.

Misadjusted PNP switch or gearshift lever linkage.

Solenoid "A" or "B" failure.

Turbine or output speed sensor failure.

Lack of pressure at start-up.

Blank PRNDL

Conditions which may cause a blank PRNDL are as follows:

The PRNDL display may be blank due to failure of PNP switch circuits "A", "B", "C", or "P", or whenthe PNP switch is out-of-adjustment or damaged.

The transmission will command the most appropriate gear range based on Reverse pressure switch andthe remaining PNP switch inputs.

ELECTRONIC COMPONENT DESCRIPTION

Transmission Control Module

A microcomputer controls the transmission by receiving and processing signals from various switches and

sensors. The microcomputer determines shift sequences, shift timing, and clutch apply and releasecharacteristics. The microcomputer is an independent controller and is referred to as the Transmission ControlModule (TCM). See Fig. 2. TCMs are available in 12-volt configurations to match the configuration of thevehicle electrical system. The pressure switch manifold and Park/Neutral Position (PNP) switch provideoperator input to the TCM. Other data sent to the TCM include throttle position; engine, turbine, and outputspeeds; and sump temperature. Any active special function, such as anti-lock brakes or power takeoff, is also aninput to the TCM. The TCM processes this data to determine proper shift points, to monitor the current gearrange, to perform ratio tests, and to compile diagnostic data. The TCM is programmed to protect the

transmission and other vehicle driveline components by inhibiting actions such as full-throttle shifts fromNeutral and high-speed direction changes. The TCM determines if a system malfunction exists and storesDiagnostic Trouble Codes (DTC) related to the malfunction. The codes, accessed by the service technician, areused in diagnosing persistent or intermittent trouble in the system.


8/501

Fig. 2: Identifying Transmission Control ModuleCourtesy of GENERAL MOTORS CORP.

Throttle Position/Torque Management

The TCM receives input on throttle position/torque management from a signal transmitted by the engineelectronic controls.

The engine electronic controls communicate directly to the transmission electronic controls over an SAE J1850or J1939 Serial Communication Interface (SCI) data link. The transmission TCM must be calibrated to receivethese signals.

Speed Sensors

There are three speed sensors typically required for use: the engine speed sensor, the turbine speed sensor, andthe output speed sensor. The speed sensors provide RPM information to the TCM. The speed ratios between thevarious sensors allow the TCM to determine the transmission operating range. Speed sensor information is alsoused to control the timing of clutch apply pressures, resulting in the best possible shift quality. Hydraulicproblems are detected by comparing the speed sensor information for the current gear range to that range'sspeed sensor information stored in the TCM memory. The speed sensors are variable reluctance devices that

CAUTION: Do not rotate the sensor in its retaining bracket. Changing the

sensor/bracket orientation may cause improper operation.


9/501

convert mechanical motion to an AC voltage. Each sensor consists of a wire coil wrapped around a pole piecethat is adjacent to a permanent magnet. These elements are contained in a housing that is mounted adjacent to arotating ferrous member. See Fig. 3.

Fig. 3: Identifying Speed Sensor

Courtesy of GENERAL MOTORS CORP.

Gear Selection

The vehicle is equipped with a column-type gearshift lever. In addition to the column gearshift lever providedfor the operator, another component associated with shift selection is the Park/Neutral Position (PNP) switchmounted on the selector shaft. See Fig. 4. The PNP switch transmits selector position information to the TCM.The PNP switch mounts directly onto the transmission housing from the outside, and detects the angular

iti f th hift l t h ft Thi iti i i t d t th TCM th t t i hi l t l


10/501

functions can be coordinated with the position of the shift controls. The PNP switch has redundant circuitry toalert the TCM in the event of a single wire or switch failure. The Neutral signal output of the PNP switch istypically used as confirmation that the transmission is in Neutral before the engine starter is engaged. The PNPswitch is interfaced to the starter circuit with weatherproof electrical connectors. The Reverse signal provisionmay be used to activate vehicle back-up lights and/or Reverse warning devices.

The operator chooses the transmission gear range by moving the gearshift lever to the appropriate gate position.

When properly adjusted, the shifter gates prevent inadvertent shifting between gear ranges, and correspond tothe internal transmission detent positions. A positive detent is provided in the transmission to maintain theselector shaft in the selected position.

The TCM shift calibration determines the available forward gear ranges for each gearshift lever position.Although specific installations vary, typical gearshift lever positions for the 1000 series are:

Park (P)- The parking pawl is engaged. The transmission is in Neutral. This position is not available on

all shift selectors. When available, may be used when starting the engine and for stationary operations.

Reverse (R)- Selected to move vehicle backward.

Neutral (N)- May be used when starting the engine and for stationary operations. The TCM disables thestarter switch if a range other than Neutral or Park is selected before starting the vehicle.

Drive (D)- The highest forward range, and is used for normal driving. The transmission shifts to 1st gearfor starting, and then automatically upshifts through the gear ranges (as operating conditions permit) untilthe highest gear range is attained.

Forward Range 4, (3), 2, 1- There are four forward gear range selector positions. The first position afterN (Neutral) is D (Drive), where all five forward gear ranges are available. Another position is first rangehold. There are three choices for the next two positions. These choices are 1-4, 1-3, and 1-2, whichdescribe the gear ranges available in that position. The vehicle manufacturer chooses the two positionsthat best fit the vocation for which the vehicle is intended.


11/501

Fig. 4: Identifying PNP SwitchCourtesy of GENERAL MOTORS CORP.

Solenoids

The control valve body contains both normally closed and normally open solenoids. A normally closed solenoidremains closed until a signal from the TCM energizes the solenoid. A normally open solenoid remains openuntil the TCM energizes the solenoid. When a solenoid valve is in the closed position, the valve blocks theflow. When a solenoid valve is in the open position, flow is permitted through the valve. The pulse widthmodulated solenoid "F" (1) and the ON/OFF shift valve solenoids "C", "D", and "E" (4), (2) and (3)

respectively, are normally closed. Both solenoid types have an orifice, electrical windings, an iron core, and asteel check ball. See Fig. 5.

The solenoids used differ in their ability to control flow or fluid pressure. The solenoids may operate in theopen or closed state with no modulation capability (solenoids "C", "D", and "E"), an intermediate flow andresultant pressure based on duty cycle (solenoid "F") or produce pressure proportional to current (solenoids "A"and "B").

Shift l id "C" "D" d "E" id th l i t di t ib t fl id t th t l t h Th hift

l id id ith f ll t l i h t t th h d f h f th di hift


12/501

solenoids provide either full control main pressure or exhaust to the head of each of the corresponding shiftvalves "C", "D", and "E". Since the valve states (stroked or unstroked) are critical to providing the correcttransmission gear range, each shift valve has a pressure switch (located in the pressure switch manifold) whichprovides feedback to the computer as to the valve's position.

Trim solenoids "A" and "B" (6) and (5) respectively, are used to control oncoming, off-going, and holdingpressure to the five clutches. These solenoids are referred to as Pressure Proportional to Current (PPC)

solenoids, since the output hydraulic pressure supplied by these solenoids is proportional to the controlledcurrent command.

Fig. 5: Identifying Shift SolenoidsCourtesy of GENERAL MOTORS CORP.

Pressure Switch Manifold

The pressure switch manifold is a multiple-switch assembly made up of three normally open pressure switches

d ll l d it h S Fi 6 N ll it h 4 3 d 2 d t hift l

"C" "D" and "E" Fluid pressures are fed from shift valves "C" "D" and "E" and the manual selector valve to


13/501

C , D and E . Fluid pressures are fed from shift valves C , D , and E and the manual selector valve tothe switches based on the positions of the valves and shift selector. The shift valve fluid pressures reflect thelogic condition at the corresponding solenoids. This logic indicates the current transmission operating range tothe TCM.

The three fluid pressure switches corresponding to the shift valves are normally open (contacts not touching)when no fluid pressure is present, so that electrical current is stopped at the switch. When fluid pressure is

routed to the switch, it moves the diaphragm and upper contact so that the contact element touches both thepositive and ground contacts. This closes the circuit and allows current to flow from the positive contact andthrough the switch.

The pressure switch (1) corresponding to Reverse is normally closed, since fluid pressure is always presentunless the selector valve is moved to Reverse. The pressure switch manifold also contains a temperature sensorthermistor (5) for sump temperature. Changes in sump fluid temperature are indicated by changes in sensorresistance (for example, increasing temperature causes decreased sensor resistance). The resistance value is then

relayed to the TCM as an input for shift control.

Fig. 6: Identifying Pressure Switch Manifold

Courtesy of GENERAL MOTORS CORP


14/501


Internal Wiring Harness

The internal wiring harness has connectors (7), (3) and (4) for the shift solenoids "C", "D" and "E". Connectors(6) and (5) go to clutch trim solenoids "A" and "B". Connector (2) goes to the torque converter clutch solenoid"F". There is also a connector (1) for the pressure switch manifold. All of these connectors go to the

transmission in-line 20-way connector (8). See Fig. 7. The transmission in-line 20-way connector transportssignals from these connectors to the TCM via the external harness.

Fig. 7: Identifying Transmission Internal Wiring HarnessCourtesy of GENERAL MOTORS CORP.

ELECTRONIC CONTROL SYSTEM

NOTE: The 6 6L diesel models use an Electronic Control Module (ECM) and 8 1L


15/501

The PCM constantly monitors the information from various sensors, and controls the systems that affect vehicleperformance and emissions. The PCM also performs the diagnostic functions for those systems. The PCM canrecognize operational problems and alert the driver through the Malfunction Indicator Lamp (MIL) when amalfunction has occurred. When a malfunction is detected, the PCM stores a Diagnostic Trouble Code (DTC)which helps to identify problem areas. This is done to aid the technician in making repairs.

SHIFT INTERLOCK SYSTEM

PROGRAMMING

FAST LEARN PROCEDURE

Overview

In general, Fast Learn is a procedure for Allison 1000 Series transmissions in which a series of tests are run toallow the Transmission Control Module (TCM) to "learn" individual clutch characteristics. Once the clutch datais learned, Fast Learn translates it to the adaptive data cells, which the TCM uses for clutch control during rangeshifts. Fast Learn is used at GM assembly plants and allows the vehicle to be driven out of the assembly plant ina near-fully-adapted state so as to minimize any customer shift complaints. The scan tool version of Fast Learnis intended to provide the same benefit following transmission repair or replacement at GM Dealerships.

Fast Learn must be used when one of the following repairs have been made to the vehicle:

Transmission replacement or internal service/overhaul.

Valve body repair or replacement, including replacement of "A" or "B" solenoids.

Transmission control module replacement.

TCM software/calibration update.

Any service in response to a shift quality complaint.

The scan tool is used to initiate Fast Learn by selecting the following commands:

F3: Special Functions.

F1: Transmission Output Controls.

Fast Learn.

NOTE: The 6.6L diesel models use an Electronic Control Module (ECM), and 8.1Lgasoline models use a Powertrain Control Module (PCM). For the purpose ofthis artic le, PCM will be used throughout to indicate all engine control modules.

A separate Transmission Control Module (TCM) is also used on models usingthe Allison transmission.

NOTE: For system description and repair information, see appropriate SHIFTINTERLOCK SYSTEMS article.

When performing Fast Learn, the following conditions must be met:


16/501

p g , g

Block drive wheels.

Apply parking brake.

Apply service brake during Drive and Reverse mode.

0% throttle, engine at idle RPM.

Transmission sump temperature at 40-100C (Reference temperature bar graph on scan tool screen).

If equipped, 4WD transfer case in 2WD.

If at any time during the procedure, required conditions are not met, Fast Learn may abort and the process willneed to be re-started from the beginning.

Description

Four steps are required to successfully complete the Fast Learn procedure:

1. Park Mode

2. Drive Mode

3. Reverse Mode

4. C2 Learn Mode

Park Mode

While the transmission is in Park with the engine idling, Fast Learn will cycle through a series of tests where C3and C4 clutches are repeatedly applied to learn their clutch characteristics. During the C3 and C4 clutchapply/release procedure, Fast Learn is able to characterize the "A" and "B" solenoid pressures corresponding toclutch return springs, and also is able to learn the volumes for C3 and C4 clutch packs. In addition, C5 clutch isrepeatedly applied and released in Park to purge out air for later learning of its clutch volume.

Drive Mode

Once all of the Park test data have converged, the scan tool instructs the driver to select Drive. Once Drive is

selected, the TCM engages C1 clutch to obtain Drive and learn C1 clutch volume. The TCM repeats this testuntil the volume learned for C1 clutch has converged.

Reverse Mode

CAUTION: While in Drive, if the scan tool loses communication, or becomesdisconnected, the vehicle may remain in Drive and could move forward ifthe wheels have not been securely blocked.

CAUTION: While in Reverse, if the scan tool loses communication, or becomesdisconnected, the vehicle may remain in Reverse and could movebackward if the wheels have not been securely blocked.

Next the scan tool instructs the driver to select Reverse. Once Reverse is selected, the TCM engages C5 clutch


17/501

g gto obtain Reverse and learn C5 clutch volume. The TCM repeats this test until the volume learned for C5 clutchhas converged.

After learning C1 and C5 clutch volume, Fast Learn updates the adaptive volume data for all shifts with eitherC1 or C5 on-coming clutch. This completes the "stationary modes" of Fast learn.

C2 Learn Mode

Following the Reverse Mode step, the scan tool exits Fast Learn and the only adaptive cells that remain to belearned are the adaptive volume data for C2 clutch. The vehicle must be driven in order to make at least three 3-4 upshifts on the same ignition cycle and at steady throttle position. This data is learned by the TCMintentionally overfilling C2 clutch. Once this overfill is corrected, C2 clutch volume is learned and all specialFast Learn actions are completely disabled.

Trouble Shooting

If Fast Learn will not run and the above-stated conditions have been met, ensure the following:

Transmission fluid temperature at 40-100C.

Closed throttle and engine at warm-idle RPM.

No active DTCs.

All speed sensors are connected and functioning properly.

NSBU switch properly adjusted and functioning.

Main pressure within specification.

TCC slip speed less than 100 RPM at idle in park/neutral.

TROUBLE SHOOTING

PRELIMINARY INSPECTION

Transmission malfunctions may be caused by poor engine performance, improper adjustments or failure ofhydraulic, mechanical or electronic components. Prior to diagnosing transmission concerns, always begin bychecking fluid level, fluid condition and shift cable adjustment. Ensure engine starts with gearshift lever in Parkand Neutral to ensure proper adjustment of park/neutral position switch. Ensure all system-related fuses are

NOTE: All shif ts wi ll be lef t in " fast" adaptive mode at th is point.

NOTE: The technician should verify that transmission shift quality for all types of shiftsis acceptable prior to releasing the vehicle to the customer.

NOTE: Any diagnosis should begin with confirming the customer's complaint. Ifpossible, road test vehicle first, and note transmission performance for future

reference during diagnosis.

okay. Check wire harnesses for proper routing. Verify all harness and component connections are clean and


18/501

tight. See WIRING DIAGRAMS. If area of fault cannot be located or repaired during preliminary inspection,check self-diagnostic system. See SELF-DIAGNOSTIC SYSTEM. Repair as necessary.

Perform road test to determine if problem has been corrected. See ROAD TESTunder PERFORMANCETESTS. If problem still exists, diagnose by symptom. See SYMPTOM DIAGNOSIS.

SYMPTOM DIAGNOSIS

Fig. 8: Excessive Slippage & Clutch ChatterCourtesy of GENERAL MOTORS CORP.

NOTE: Perform PRELIMINARY INSPECTION prior to diagnosing by symptom.

NOTE: Use the following symptoms to aid in preliminary diagnosis. See Fig. 8 -Fig. 27 .If a listed symptom matches the customer's concern, check the applicableitems for possible cause.


19/501

Fig. 9: Fluid Leaks From Fluid Fill Tube & VentCourtesy of GENERAL MOTORS CORP.

Fig. 10: Fluid Leaks From Transmission InputCourtesy of GENERAL MOTORS CORP.

Fig. 11: Fluid Leaks From Transmission OutputCourtesy of GENERAL MOTORS CORP.


20/501

Fig. 12: Intermittent Buzzing NoiseCourtesy of GENERAL MOTORS CORP.

Fig. 13: Low Main Line Pressure In All Gear Ranges (1 Of 2)Courtesy of GENERAL MOTORS CORP.

Fig. 14: Low Main Line Pressure In All Gear Ranges (2 Of 2)Courtesy of GENERAL MOTORS CORP.

Fig. 15: Low Main Line Pressure In Specific Gear Ranges, Normal In All Other Gear RangesCourtesy of GENERAL MOTORS CORP.


21/501

Fig. 19: Excessive Flare - Engine Overspeed On Wide-Open Throttle (2 Of 2) Courtesy of GENERAL MOTORS CORP


22/501


Fig. 20: High Stall Speeds (Stall In Ranges 1-5)Courtesy of GENERAL MOTORS CORP.

Fig. 21: Low Stall Speeds (Stall In Ranges 1-5)Courtesy of GENERAL MOTORS CORP.

Fig. 22: Transmission Will Not Make A Specific ShiftCourtesy of GENERAL MOTORS CORP.


23/501

Fig. 23: Transmission Will Not Stay In Forward Or ReverseCourtesy of GENERAL MOTORS CORP.

Fig. 24: Transmission Will Not Shift To Forward Or ReverseCourtesy of GENERAL MOTORS CORP.

Fig. 25: Transmission OverheatsCourtesy of GENERAL MOTORS CORP.


24/501

Fig. 26: Transmission Does Not Shift ProperlyCourtesy of GENERAL MOTORS CORP.

Fig. 27: Abnormal Activities Or ResponsesCourtesy of GENERAL MOTORS CORP.

CLUTCH APPLICATIONS


25/501

Fig. 28: Clutch & Solenoid Chart (1 Of 2)Courtesy of GENERAL MOTORS CORP.


26/501

Fig. 29: Clutch & Solenoid Chart (2 Of 2)Courtesy of GENERAL MOTORS CORP.

PERFORMANCE TESTS

ROAD TEST

The following test provides a method of evaluating the condition of the automatic transmission. The test isstructured so that most driving conditions would be achieved. The test is divided into the following parts:

Electrical Function Check

Upshift Control and TCC Apply

Part Throttle Detent Downshifts

CAUTION: Complete the test in the sequence given. Incomplete testing cannotguarantee an accurate evaluation.

Full Throttle Detent Downshifts

Manual Downshifts


27/501

Manual Downshifts

Coasting Downshifts

Manual Gear Range Selection

Before the road test, ensure the following:

The engine is performing properly.

Transmission fluid level is correct.

Tire pressure is correct.

During the road test:

Perform the test only when traffic conditions permit. Operate the vehicle in a controlled, safe manner.

Observe all traffic regulations.

View the scan tool data while conducting this test. Take along qualified help in order to operate thevehicle safely.

Observe any unusual sounds or smells.

After the road test, check the following:

Transmission fluid level.

DTCs that may have set during the testing. Refer to the applicable DTC.

Scan tool data for any abnormal readings or data.

Electrical Function Check

Perform this check first, to ensure the electronic transmission components are connected and functioningproperly. If these components are not checked, a simple electrical condition could be mis-diagnosed.

1. Connect the scan tool.

2. Ensure the gearshift lever is in Park and set the parking brake.

3. Start the engine.

4. Verify that the following scan tool data can be obtained and is functioning properly. Data that is

questionable may indicate a concern.

Engine Speed

Transmission Input Speed

Transmission Output Speed

Vehicle Speed

"C", "D", "E" & Reverse Pressure Switch States


28/501

E. Verify that all gearshift lever positions match the scan tool display.

8. Check throttle angle input in the following order:


29/501

g p g

A. Apply the brake pedal and ensure the parking brake is set.

B. Ensure the gearshift lever is in Park.

C. Monitor throttle angle while increasing and decreasing engine speed with the throttle pedal. Thescan tool throttle angle should increase and decrease with engine speed.

If any of the above checks do not perform properly, record the result for reference after completion of the roadtest.

Upshift Control & Torque Converter Clutch Apply

The TCM calculates the upshift points based on throttle angle and the engine, turbine and output speed. Whenthe TCM determines that conditions are met for a shift to occur, the TCM commands the shift and controls

solenoid "A" and "B" current to properly control clutch pressures during the shift.

1. Choose a throttle angle of 10, 25 or 50 percent. All throttle angles shown should be tested to cover thenormal driving range.

2. Monitor the following scan tool parameters:

Throttle Angle

Vehicle Speed

Engine Speed

Output Shaft Speed

Commanded Gear

Slip Speed

Solenoid States

3. Place the gearshift lever in the Drive position.

4. Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.5. As the transmission upshifts, note the vehicle speed when the shift occurs for each gear change. There

should be a noticeable shift feel or engine speed change within 1-2 seconds of the commanded gearchange.

6. Compare the shift speeds to the shift speed chart. Shift speeds may vary slightly due to transmission fluidtemperature or hydraulic delays in responding to electronic controls. Note any harsh, soft or delayedshifts or slipping. Note any noise or vibration.

7. Repeat steps 1 -6 to complete all throttle angles.8. Check for TCC apply in 2nd, 3rd, 4th and 5th gear. Note the TCC apply point. When the TCC applies,

there should be a noticeable drop in engine speed and a drop in slip speed to below 100 RPM. If the TCCapply can not be detected, check for DTCs. Lightly tap and release the brake pedal. The TCC will release.

Part Throttle Detent Downshift



30/501

The shift solenoids control the upshifts in the manual gear ranges.

NOTE: Perform the following tests using 10 percent to 15 percent throttle angle


31/501

Reverse

1. With the vehicle stopped, move the gearshift lever to Reverse.

2. Slowly accelerate the vehicle.

3. Verify that there is no noticeable slip, noise or vibration.

Manual First

1. With the vehicle stopped, move the gearshift lever to 1st.

2. Accelerate the vehicle to 20 MPH.

3. Verify no upshifts occur, the TCC does not apply and there is no noticeable slip, noise, or vibration.

Manual Second

1. With the vehicle stopped, move the gearshift lever to 2nd.


3. Verify the 1-2 shift occurs, the 2-3 shift does not occur and there is no noticeable slip, noise or vibration.

Manual Third

1. With the vehicle stopped, move the gearshift lever to 3rd.


3. Verify the 1-2 shift occurs, the 2-3 shift occurs and there is no noticeable slip, noise or vibration.

SHIFT SPEED SPECIFICATIONS

Fig. 30: 1-2 & 2-3 Shift Speed SpecificationsCourtesy of GENERAL MOTORS CORP.

NOTE: Perform the following tests using 10 percent to 15 percent throttle angle.


32/501

Fig. 31: 3-4 & 4-5 Shift Speed SpecificationsCourtesy of GENERAL MOTORS CORP.

TORQUE CONVERTER DIAGNOSIS

The Torque Converter Clutch (TCC) is applied by fluid pressure, which is controlled by a PWM solenoid valve.This solenoid valve is located inside of the automatic transmission assembly. The solenoid valve is controlledthrough a combination of computer controlled switches and sensors.

Torque Converter Stator

The torque converter stator roller clutch can have two different malfunctions.

The stator assembly freewheels in both directions.

The stator assembly remains locked up at all times.

Poor Acceleration At Low Speed

If the stator is freewheeling at all times, the vehicle tends to have poor acceleration from a standstill. At speedsabove 30-35 MPH, the vehicle may act normally. For poor acceleration, you should first determine that theexhaust system is not blocked, and the transmission is in 1st gear when starting out.

If the engine freely accelerates to high RPM in Neutral, you can assume that the engine and the exhaust systemare normal. Check for poor performance in Drive and Reverse to help determine if the stator is freewheeling atall times.

Poor Acceleration At High Speed

If the stator is locked up at all times, performance is normal when accelerating from a standstill. Engine RPMand vehicle speed are limited or restricted at high speeds. Visual examination of the converter may reveal a bluecolor from overheating.

If the converter has been removed, you can inspect the stator roller clutch by inserting a finger into the splined

inner race of the roller clutch and trying to turn the race in both directions. You should be able to freely turn theinner race clockwise, but you should have difficulty in moving the inner race counterclockwise or you may beunable to move the race at all.


33/501

Whine Noise

You may notice a torque converter whine when the vehicle is stopped and the transmission is in Drive orReverse. This noise will increase as you increase the engine RPM. The noise will stop when the vehicle ismoving or when you apply the torque converter clutch, because both halves of the converter are turning at thesame speed.

Perform a stall test to make sure the noise is actually coming from the converter:

1. Place your foot on the brake.


3. Depress the accelerator to approximately 1200 RPM for no more than 6 seconds. Listen for torqueconverter noise. A torque converter noise will increase under this load.

Torque Converter Clutch Shudder

The key to diagnosing Torque Converter Clutch (TCC) shudder is to note when it happens and under whatconditions.

TCC shudder which is caused by the transmission should only occur during the apply or the release of theconverter clutch. Shudder should never occur after the TCC plate is fully applied.

If the shudder occurs while the TCC is applying, the problem can be within the transmission or the torqueconverter. Something is causing one of the following conditions to occur:

Something is not allowing the clutch to become fully engaged.

Something is not allowing the clutch to release. The clutch is releasing and applying at the same time.

One of the following conditions may be causing the condition to occur:

Leaking turbine shaft seals.

A restricted release orifice.

NOTE: Do not confuse this noise with pump whine noise, which is usually noticeable in

Park, Neutral and all other gear ranges. Pump whine wil l vary wi th line pressure.

CAUTION: You may damage the transmission if you depress the accelerator formore than 6 seconds.

Defective friction material on the TCC piston.

If Shudder Occurs After TCC Has Applied


34/501

pp

If shudder occurs after the TCC has applied, most of the time there is nothing wrong with the transmission.

As mentioned above, the TCC is not likely to slip after the TCC has been applied. Engine problems may go

unnoticed under light throttle and load, but they become noticeable after the TCC apply when going up a hill oraccelerating. This is due to the mechanical coupling between the engine and the transmission.

Once TCC is applied, there is no torque converter, fluid coupling, assistance. Engine or driveline vibrationscould be unnoticeable before TCC engagement.

Inspect the following components to avoid misdiagnosis of TCC shudder. An inspection will also avoid theunnecessary disassembly of a transmission or the unnecessary replacement of a torque converter.

Spark Plugs- Inspect for cracks, high resistance or a broken insulator.

Plug Wires- Look in each end. If there is red dust (ozone) or a black substance (carbon) present, thewires are bad. Also look for a white discoloration of the wire. This indicates arcing during hardacceleration.

Coil- Look for a black discoloration on the bottom of the coil. This indicates arcing while the engine ismisfiring.

Fuel Injector- The filter may be plugged.Vacuum Leak- The engine will not get a correct amount of fuel. The mixture may run rich or leandepending on where the leak occurs.

EGR Valve- The valve may let in too much or too little unburnable exhaust gas, and could cause theengine to run rich or lean.

MAP/MAF Sensor- Like a vacuum leak, the engine will not get the correct amount of fuel for properengine operation.

Carbon On Intake Valves- Carbon restricts the proper flow of air/fuel mixture into the cylinders.Flat Cam- Valves do not open enough to let the proper fuel/air mixture into the cylinders.

Oxygen Sensor- This sensor may command the engine too rich or too lean for too long.

Fuel Pressure- This may be too low.

Engine Mounts- Vibration of the mounts can be multiplied by TCC engagement.

Axle Joints- Check for vibration.

TP Sensor- The TCC apply and release depends on the TP sensor in many engines. If the TP sensor isout of specification, TCC may remain applied during initial engine loading.

Cylinder Balance- Bad piston rings or poorly sealing valves can cause low power in a cylinder.

Fuel Contamination- This causes poor engine performance.

HYDRAULIC PRESSURE TESTS

Line Pressure

WARNING: Keep the brakes applied at all times to prevent unexpected vehiclemotion. Personal injury may result if the vehicle moves unexpectedly.


35/501

Checking main line pressure helps to determine if a transmission malfunction is due to a mechanical or anelectrical problem. Properly making these pressure checks requires transmission and vehicle preparation,recording of data, and comparing recorded data against specifications provided.

1. Remove the oil pressure tap plug. Install Pressure Test Adapter Fitting (J-45056) prior to connecting theoil pressure gauge. See Fig. 32.

2. Check the transmission fluid level. See SERVICING - "C" & "K" SERIES (ALLISON)article. Alltransmission fluid level and pressure checks must be made at normal operating temperatures of 160-200F (71-93C).

3. Connect a 0-300 psi (0-21.1 kg/cm2) oil pressure gauge to the pressure test adapter fitting. Use the scantool to check the engine RPM. See Fig. 33.

4. With the brakes applied, record the line pressure values at 600 RPM in Neutral and Reverse. Thetransmission will be in converter mode (torque converter clutch not applied).

5. With the brakes applied, record the line pressure values with the engine running at 2100 RPM in Neutral.The transmission will be in converter mode (torque converter clutch not applied).

6. With the brakes applied, use the following scan tool settings to check pressures in 1st through 5th gearranges at 600 RPM. The transmission will be in converter mode (torque converter clutch not applied) at600 RPM.

A. Select - F0: Diagnostics and press ENTER.

B. Select - Model Year.

C. Select - LDTrk, MPV, Incomplete.

D. Select - F0: Powertrain, press ENTER.

E. Select - Engine size, press ENTER.

F. Select - 5 Speed Automatic, press ENTER.

G. Select - F2: Special Functions, press ENTER.H. Select - F1: Transmission Output Controls.

I. Select - Shift transmission. This will allow the technician to shift the transmission and check linepressure in each forward gear range.

7. Compare the data recorded to the line pressure specifications. See Fig. 33.

8. Disconnect the oil pressure gauge and remove the pressure test adapter fitting.

9. Reinstall the oil pressure tap plug using NEW "O" ring. Tighten the plug to 106 INCH lbs. (12 N.m).


36/501

Fig. 32: Checking Line PressureCourtesy of GENERAL MOTORS CORP.

Fig. 33: Line Pressure SpecificationsCourtesy of GENERAL MOTORS CORP.

CLUTCH TEST

Introduction

Clutch test allows the technician to manually select each of the five forward gear ranges with the vehiclestopped. The intent of this procedure is to verify the ability of all five clutches to transmit torque withoutslipping. See CLUTCH & SOLENOID APPLICATIONSunder TROUBLE SHOOTING.


37/501

Test Procedure

Use the scan tool to perform the clutch test. Select the following information when setting up the scan tool for

running the test. Use the shift transmission feature on the scan tool to complete the clutch test.

1. Select - F0: Diagnostics and press ENTER.

2. Select - Model Year (i.e., 1 = 2001).

3. Select - LDTrk, MPV, Incomplete.

4. Select - F0: Powertrain, press ENTER.

5. Select - Engine size, press ENTER.

6. Select - 5 Speed Automatic, press ENTER.7. Select - F2: Special Functions, press ENTER.

8. Select - F1: Transmission Output Controls.

9. Select - Shift transmission. This will allow the technician to shift the transmission and check the integrityof each clutch in the transmission.

Attach the transmission pressure gauge as described in line pressure check procedure. See HYDRAULIC

PRESSURE TESTS. Apply parking brake and hold service brakes and increase engine speed to 1400 RPM.Using scan tool, select UPSHIFT and shift transmission from 1st gear range sequentially to 5th gear range,while observing turbine speed. Turbine speed should increase momentarily and then drop to zero RPM wheneach gear range is attained. Line pressure should drop momentarily then regain pressure when each gear rangeis attained.

Maintain 1400 RPM, select the DOWNSHIFT soft key and downshift transmission from 5th gear rangesequentially to 1st gear range while observing turbine speed. Turbine speed should increase momentarily and

then drop to zero RPM when each gear range is attained.

To further investigate a suspected leak in a clutch circuit, the clutch test should be repeated keeping engine atidle speed. While performing clutch test at 600 RPM, main pressure should drop momentarily, then regainpressure when each gear range is attained. If main pressure remains low, suspect damaged seal in that gearrange. If low pressure is in 1st gear range only, suspect C5 piston seal damage.

SELF-DIAGNOSTIC SYSTEM

DIAGNOSTIC SYSTEM CHECK

Circuit Description

The diagnostic system check is an organized approach to identify a condition created by the automatictransmission. The diagnostic system check is the diagnostic starting point for a automatic transmissioncom laint. The dia nostic s stem check directs ou to the next lo ical ste for dia nosin a transmission

concern. Perform this check only if there is a driveability complaint or if you have been directed here fromanother service information section.

Test Description


38/501

Test Description

The numbers listed below refer to step numbers in the diagnostic procedure:

1- This step determines if the scan tool is receiving power through the DLC connector.2- The MIL should illuminate whenever the ignition is on and the engine is not running.

3- This step determines if the TCM is transmitting class 2 serial data to the DLC and that the class 2 datacircuit is not open or shorted.

4- This step determines if a DTC is current or stored in history.

Diagnostic Procedure

1. Turn ignition on, engine off. Does the scan tool turn on? If so, go to next step. If not, diagnose scan toolconcern. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.

2. Is the MIL on? If so, go to next step. If not, diagnose MIL concern. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

3. Attempt to establish communication with the TCM. Does the scan tool communicate with the TCM? Ifso, go to next step. If not, diagnose scan tool concern. See appropriate BODY CONTROL MODULESarticle in ACCESSORIES & EQUIPMENT.

4. Use the scan tool CAPTURE INFO function to save or capture (store information) any DTC information.Are there any DTCs present? If so, see DIAGNOSTIC TROUBLE CODE DEFINITIONS. If not, seeSYMPTOM DIAGNOSISunder TROUBLE SHOOTING.

Diagnostic Aids

NOTE: Check for applicable service bulletins before proceeding with this test. Performthis test only if there is a driveability complaint or if you have been directed tothis table from another section in the service information.

NOTE: Do not turn the ignition off when performing this diagnostic procedure. Do notclear the DTCs unless instructed by this diagnostic procedure.

NOTE: Diagnostic Trouble Codes (DTC), engine performance, and transmissiondefault actions can greatly affect the transmission performance. Ensurethat these items are not the cause of a transmission concern.

NOTE: DO NOT clear the DTC unless directed by a diagnostic procedure. Clearing theDTCs will erase all freeze frame and failure records stored in PCM memory.

NOTE: Poor engine performance can sometimes be diagnosed as a transmission

driveability condition. To avoid mis-diagnosis of the automatic transmission,always perform powertrain d iagnostic system check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.


39/501

Use a scan tool that is known to function correctly. If necessary, test the scan tool on another vehicle.

Ensure the scan tool contains the most current file available.

The scan tool will display a loss of communication error message under the following conditions:TCM power is interrupted.

The ignition is turned off.

The battery voltage level is very low.

A poor connection at the Diagnostic Link Connector (DLC).

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE DEFINITIONS (1)

NOTE: Only transmission-related DTCs are listed. For engine-related DTC definitions,see appropriate SELF-DIAGNOSTICS art icle in ENGINE PERFORMANCE. TheseDTCs pertain to engine performance and must be repaired firs t, as engineperformance and related component signals wi ll affect transaxle operation anddiagnosis.

DTC (2) Description

P0218 Transmission Fluid Over Temperature

P0500 Vehicle Speed Sensor Circuit

P0561 Unrealistic Variations In Vehicle System Voltage

P0562 System Voltage Low

P0563 System Voltage High

P0700 MIL Illumination RequestedP0701 Transmission Control System Performance

P0703 Brake Switch Circuit

P0708 Transmission Range Sensor Circuit High Input

P0711 Transmission Fluid Temperature Sensor Circuit - Performance

P0712 Transmission Fluid Temperature Sensor Circuit - Low Input (High Temperature)

P0713 Transmission Fluid Temperature Sensor Circuit - High Input (Low Temperature)

P0716 Turbine Speed Sensor Circuit - PerformanceP0717 Turbine Speed Sensor Circuit - No Signal

P0721 Output Speed Sensor Circuit - Performance

P0722 Output Speed Sensor Circuit - No Signal

P0726 Engine Speed Sensor Circuit - Performance

P0727 Engine Speed Sensor Circuit - No Signal

P0731 Incorrect 1st Gear Ratio


40/501

CLEARING DIAGNOSTIC TROUBLE CODES

Using scan tool, clear DTCs following scan tool manufacturer's instructions. Do not clear DTCs unlessinstructed to do so.


41/501

SUMMARY

If no hard DTCs are present, and driveability symptoms or intermittent DTCs exist, attempt diagnosis bysymptom, or by testing individual components related to system fault. See TROUBLE SHOOTING. If noproblem is found, verify proper electronic control system circuit operation.

DIAGNOSTIC TESTS

DTC P0218: TRANSMISSION FLUID OVER TEMPERATURE

Circuit Description

The Transmission Fluid Temperature (TFT) sensor is a part of the transmission pressure switch manifoldassembly. The TFT sensor is a thermistor which changes its value based on temperature. The TransmissionControl Module (TCM) supplies a 5-volt reference signal to the TFT sensor. When the transmission fluid iscold, the sensor resistance is high and the TCM detects a high signal voltage. As transmission fluid temperatureincreases, the resistance becomes less, and the signal voltage decreases.

This is a type "C" DTC.

Conditions For Running The DTC

DTC will run under the following condition:

The components are powered, and ignition voltage is greater than 9 volts and less than 18 volts.

Engine speed is greater than 200 RPM and less than 7500 RPM for 5 seconds.

Conditions For Setting The DTC

DTC will set under the following condition:

DTC sets when the TCM detects a transmission fluid temperature greater than 259F (126C) for 10seconds.

NOTE: Always clear DTCs once repairs are complete. See CLEARING DIAGNOSTICTROUBLE CODES . Road test vehicle and retrieve DTCs to determine ifcomplaint or DTC is repaired.

NOTE: For circuit identification, see CONNECTOR IDENTIFICATION and WIRINGDIAGRAMS .

Action Taken When The DTC Sets

TCM performs the following actions if DTC is set:


42/501

DTC is stored in the TCM history.

The TCM freezes shift adapts.

The TCM inhibits TCC engagement.

Conditions For Clearing The DTC

DTC will clear under the following conditions:

A scan tool can clear the DTC from the TCM history.

The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-upcycles without failure.

Test Description


4- This step tests for ignition voltage.

5- This step tests for unrealistic changes in transmission fluid temperature.

6- This step tests the internal wiring harness.7- This step checks the wiring harness for opens or shorts.

9- This step tests the resistance of the TFT sensor.


1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTICSYSTEM CHECKunder SELF-DIAGNOSTIC SYSTEM.

2. Inspect the engine cooling system for air flow restrictions, air flow blockage or debris. Inspect thetransmission cooling system for air flow restrictions, air flow blockage, damaged cooler lines or hoses,and low transmission fluid cooler flow. Did you perform the inspection and correct the conditions ifnecessary? If so, go to next step. If not, see SERVICING - "C" & "K" SERIES (ALLISON)article.

3. Check the transmission fluid level. Is the transmission fluid level correct? If so, go to next step. If not, seeSERVICING - "C" & "K" SERIES (ALLISON)article.

4. Install the scan tool. Turn ignition on, engine off. Record DTC and failure records. Start the engine.

Using the scan tool, check ignition voltage. Is the voltage 9-18 volts? If so, go to next step. If not, seeDTC P0562: SYSTEM VOLTAGE LOWor DTC P0563: SYSTEM VOLTAGE HIGH.

5. Turn the ignition on, engine off. Using scan tool, monitor transmission fluid temperature. Start the engineand drive the vehicle under normal operating conditions or in the specific operating mode when theovertemperature condition occurred if known. Do the transmission fluid temperature readings appearinconsistent or exceed 250F (121C)? If so, go to next step. If not, see DIAGNOSTIC AIDS.

6. Disconnect transmission in-line 20-way connector. Using a DVOM, measure the resistance of the TFT

sensor between transmission in-line 20-way connector terminals "G" and "H". Is the resistance within thespecified range? See COMPONENT RESISTANCEunder ELECTRONIC COMPONENTSPECIFICATIONS. If so, go to next step. If not, go to step 9 .

7. Reconnect the transmission in-line 20-way connector. Disconnect the TCM C2 connector. Measure the


43/501

yresistance between TCM connector C2 terminals No. 10 and 20. Is the resistance within the specifiedrange? See COMPONENT RESISTANCEunder ELECTRONIC COMPONENT SPECIFICATIONS.If so, go to step 12 . If not, go to next step.

8. Inspect and repair the transmission wiring harness assembly. Is the repair complete? If so, go to step 13 .9. Remove the pressure switch manifold. See PRESSURE SWITCH MANIFOLDunder REMOVAL &

INSTALLATION. Measure the resistance between pressure manifold switch terminals "E" and "F". Is theresistance within the specified range? See COMPONENT RESISTANCEunder ELECTRONICCOMPONENT SPECIFICATIONS. If so, go to next step. If not, go to step 11 .

10. Replace the internal wiring harness. See TRANSMISSION INTERNAL WIRING HARNESSunderREMOVAL & INSTALLATION. Is the replacement complete? If so, go to step 13 .

11. Replace the pressure switch manifold. See PRESSURE SWITCH MANIFOLDunder REMOVAL &INSTALLATION. Is the replacement complete? If so, go to step 13 .

12. Replace the TCM. See TRANSMISSION CONTROL MODULEunder REMOVAL &INSTALLATION. Is the replacement complete? If so, go to next step.

13. Perform the following procedure to verify the repair:

Clear the DTC.

Using the scan tool, monitor the transmission fluid temperature.

Drive the vehicle under normal operating conditions or in the specific operating mode where theovertemperature condition occurred if known.

Did the DTC return? If so, go to step 1 . If not, system is okay.

Diagnostic Aids

Inspect the wiring for poor electrical connections at the TCM. Look for a bent, backed-out or damaged terminal,poor terminal tension, a chafed wire or a broken wire inside the insulation. When diagnosing for an intermittentshort or open, massage the wiring harness while watching the test equipment for a change. Drive the vehicle ifnecessary to experience a fault.

DTC P0500: VEHICLE SPEED SENSOR CIRCUIT

Circuit Description

CAUTION: In most cases, the TCM is not at fault. Investigate thoroughly beforereplacing the TCM.


The Vehicle Speed Sensor (VSS) monitors the rotation speed of the transmission output shaft. The VSSassembly is a permanent magnet generator. It produces an AC voltage as the rotor teeth on the output shaft ofthe transmission (2WD) or transfer case (4WD) pass through the sensor's magnetic field. The AC voltagefrequency and amplitude increase as the vehicle speed increases. The TCM will send a controlled duty cycle

lt t th PCM th t t i f 4 5 lt 5 0 lt Th PCM t thi i l i t hi l


44/501

voltage to the PCM that operates in a range of -4.5 volts or 5.0 volts. The PCM converts this signal into vehiclespeed. As vehicle speed increases, the frequency of the duty cycle will increase.

This is a type "B" DTC.



Engine running.



If the PCM detects a difference in vehicle speed with the VSS of more than 5 MPH, then DTC P0500 isset.


PCM performs the following actions if DTC is set:

The PCM illuminates the MIL on the second consecutive drive trip that the diagnostic runs.

The PCM disables cruise control.

The PCM records the operating conditions when the conditions for setting the DTC are met. The PCMstores this information as freeze frame and failure records.

The PCM stores DTC P0500 in PCM history.



The PCM turns off the MIL during the third consecutive trip in which the diagnostic test runs and passes.

A scan tool can clear the DTC.

The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without anemission-related diagnostic fault occurring.

The PCM cancels the DTC default actions when the ignition is off long enough to power down the PCM.

Test Description


4- This step tests the TCM and circuit 400 for voltage at the PCM connector.

5- This step tests for continuity and a short to ground in the wiring system between the TCM and PCM.



45/501

g


2. Install a scan tool. Turn ignition on, engine off. Record the DTC freeze frame and failure records. Clearthe DTC. Is there a DTC P0721 or P0722 present? If so, see DTC P0721: OUTPUT SPEED SENSORCIRCUIT - PERFORMANCEor DTC P0722: OUTPUT SPEED SENSOR CIRCUIT - NOSIGNAL. If not, go to next step.

3. Raise and support the vehicle. Start and idle the engine. Turn off the traction control system, if equipped.Select and monitor VSS on the scan tool. Place the gearshift lever in Drive position. With the drivewheels rotating, slowly increase the engine speed. Does vehicle speed on the scan tool increase withwheel speed? If so, see DIAGNOSTIC AIDS. If not, go to next step.

4. Turn engine off. Disconnect connector C2 at the PCM. Turn ignition on. Using a DVOM and TerminalTest Kit (J-35616-A), test the signal circuit (400) for voltage between PCM connector C2 terminal No. 21and ground. Is the circuit voltage 4-5 volts? If so, go to step 7 . If not, go to next step.

5. Turn ignition off. Test the signal circuit (400) between the TCM and PCM for an open or a short toground. Did you find and correct a condition? If so, go to step 8 . If not, go to next step.

6. Replace the TCM. See TRANSMISSION CONTROL MODULEunder REMOVAL &INSTALLATION. Did you complete the replacement? If so, go to step 8 .

7. Replace the PCM. See POWERTRAIN CONTROL MODULEunder REMOVAL &INSTALLATION. Did you complete the replacement? If so, go to next step.


Select the DTC.

Select CLEAR INFO.

Operate the vehicle within the conditions for running the DTC.

Select TRANSMISSION SPECIFIC DTC. Enter DTC P0500.

Has the test run and passed? If so, system is okay. If not, go to step 1 .

Diagnostic Aids

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension.

Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiringharness while watching scan tool for change in value.

DTC P0561: UNREALISTIC VARIATIONS IN VEHICLE SYSTEM VOLTAGE


Circuit Description

The Transmission Control Module (TCM) requires ignition voltage to operate. Ignition voltage is provided bypins No. 102 and 104 of the ignition switch.


46/501




The test becomes enabled when the engine has been running above 400 RPM for at least 0.5 second.

The components are powered, and ignition voltage is greater than 9.0 volts and less than 18 volts.



This test detects unrealistic variations in ignition voltage over the entire range of voltage. DTC will setwhen voltage drops below 6.5 volts at either Force Motor (TCM Driver) or ignition input for 1.5 seconds,or when the voltage variation limit of 4.0 volts or over is detected at either the Force Motor (TCM Driver)or ignition input.


When DTC is active, the following conditions will occur:

Transmission will fail to Neutral.






Test Description


2- This step uses a substitute TCM to identify whether the original TCM was causing a voltage spike.

3- This step is done to identify the source of excessive voltage variation.



2. This DTC indicates an unacceptable variation in ignition voltage or TCM driver voltage. If available,replace the TCM with a known-good substitute TCM. Clear the DTC and drive the vehicle. Did the DTC


47/501

return? If so, go to next step. If not, go to step 4 .

3. Find and repair the source of the voltage variation. Is the repair complete? If so, go to step 5 .


5. Drive the vehicle to verify repair. Did the DTC return? If so, go to step 1 . If not, system is okay.

Diagnostic Aids

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension.Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiringharness while watching scan tool for change in value.

DTC P0562: SYSTEM VOLTAGE LOW

Circuit Description

The Transmission Control Module (TCM) requires ignition voltage to operate correctly. The voltage signalshould be direct from the ignition switch to avoid any interference.





The engine speed is greater than 400 RPM for one second.



DTC sets when the TCM detects a voltage less than 8 volts for 5 seconds.





While diagnostic response is active, if the gearshift lever is moved to a forward gear range, the


48/501

W g p , g g g ,transmission will shift to Neutral, 3rd, or 5th gear; if the gearshift lever is moved to Neutral, transmissionwill shift to Neutral; and if the gearshift lever is moved to Reverse, transmission will shift to Neutral orReverse (fail to range/hydraulic defaults).

DTC will be stored in the TCM history.



Illuminates MIL when active.





Test Description


2- This step tests for battery voltage.

4- This step tests the status of the charging system.

6- This step tests charging system voltage.

7- This step tests voltage available at the TCM.



2. Install the scan tool. Turn ignition on, engine off. Record the DTC failure records. Using a DVOM,measure and record the voltage across the battery terminals. Is the voltage greater than 10.5 volts? If so,go to step 4. If not, go to next step.

3. Replace the battery or resolve the battery condition. Is the condition resolved or replacement complete? Ifso, go to step 10 .

4. Start the engine and warm to normal operating temperature. Is the alternator lamp on? If so, go to nextstep. If not, go to step 6 .

5. Repair the charging system. See appropriate GENERATORS & REGULATORS article in STARTING &CHARGING SYSTEMS. Is the repair complete? If so, go to step 10 .

6. Increase the engine speed to 1000-1500 RPM. Observe the system voltage on the scan tool. Is the voltage

13-15 volts? If so, go to next step. If not, go to step 5 .

7. Turn ignition off. Disconnect TCM C1 connector. Additional DTCs may set. Turn ignition on, engine off.Install Breakout Box (J-39700) and Breakout Box Adapter (J-43799). Using a DVOM, measure thevoltage between TCM connector C1 terminals No. 2 and 1, 3 and 1, and 4 and 1. Then measure voltage atTCM connector C1 terminals No 2 and 5 3 and 5 and 4 and 5 Compare the battery voltage to the wire


49/501

TCM connector C1 terminals No. 2 and 5, 3 and 5, and 4 and 5. Compare the battery voltage to the wirevoltage. Is the voltage difference greater than 0.5 volt? If so, go to next step. If not, go to step 9 .

8. Inspect the transmission wiring harness assembly. Repair as necessary. Is the repair complete? If so, go to

step 10 .9. Replace the TCM. See TRANSMISSION CONTROL MODULEunder REMOVAL &

INSTALLATION. Is the replacement complete? If so, go to next step.

10. Perform the following procedure to verify the repair: Clear the DTC.

Start the engine and warm to normal operating temperature.

The system voltage should be 10-16 volts.


Diagnostic Aids

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension.Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiringharness while watching scan tool for change in value.

DTC P0563: SYSTEM VOLTAGE HIGH

Circuit Description

The Transmission Control Module (TCM) requires ignition voltage to operate correctly. The voltage signalshould be direct from the ignition switch to avoid any interference.







The engine speed is greater than 450 RPM for one second.




50/501


DTC sets when the TCM detects a voltage greater than 16 volts for 6 seconds.



While diagnostic response is active, if the gearshift lever is moved to a forward gear range, transmissionwill shift to Neutral, 3rd, or 5th gear; if the gearshift lever is moved to Neutral, transmission will shift toNeutral; and if the gearshift lever is moved to Reverse, transmission will shift to Neutral or Reverse (fail

to range/hydraulic defaults). DTC will be stored in the TCM history.



Illuminates MIL when active.





Test Description


2- This step tests battery voltage.

4- This step tests the status of the charging system.

6- This step tests charging system voltage.

7- This step tests voltage available at the TCM.



2. Install the scan tool. Turn ignition on, engine off. Record the DTC failure records. If other DTCs arepresent, refer to the applicable diagnostic test before continuing. Using a DVOM, measure and record the

voltage across the battery terminals. Is the voltage 10.5-14 volts? If so, go to step 4 . If not, go to nextstep.

3. Replace the battery or resolve the battery condition. Is the replacement complete or condition resolved? Ifso, go to step 10 .

4 Start the engine and warm to normal operating temperature Is the alternator lamp on? If so go to next


51/501

4. Start the engine and warm to normal operating temperature. Is the alternator lamp on? If so, go to nextstep. If not, go to step 6 .

5. Repair the charging system. See appropriate GENERATORS & REGULATORS article in STARTING &

CHARGING SYSTEMS. Is the repair complete? If so, go to step 10 .

6. Increase the engine speed to 1000-1500 RPM. Observe the system voltage on the scan tool. Is the voltage13-15 volts? If so, go to next step. If not, go to step 5 .

7. Turn ignition off. Disconnect the TCM connector C1 from the TCM (additional DTCs may set). Turnignition on, engine off. Install a Breakout Box (J-39700) and Breakout Box Adapter (J-43799). Using aDVOM, measure the voltage between TCM connector C1 terminals No. 2 and 1, 3 and 1, and 4 and 1.Then measure voltage between connector C1 terminals No. 2 and 5, 3 and 5, and 4 and 5. Compare the

battery voltage (recorded in step 2 to the wire voltage. Is the voltage difference greater than 0.5 volt? Ifso, go to next step. If not, go to step 9 .

8. Inspect the wiring for the source of the high resistance condition. Manipulate the harness to check forintermittent short or open. Repair or replace the faulty wiring. Is the repair complete? If so, go to step 10 .



Clear the DTC.

Start the engine and warm to normal operating temperature.

The system voltage, as indicated by the scan tool, should be 10-16 volts.

Check for the DTC.


Diagnostic Aids

Inspect wiring for poor connections. Check for bent, backed out or damaged terminals, or poor terminal tension.Check for chafed wire or broken wire inside insulation. When diagnosing intermittent condition, wiggle wiring

harness while watching scan tool for change in value.

DTC P0700: MIL ILLUMINATION REQUESTED


NOTE: To locate components, see COMPONENT LOCATIONS in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. For circuit reference, seeappropriate WIRING DIAGRAMS article. For connector terminal identification,

Description

see CONNECTOR IDENTIFICATION in appropriate SELF-DIAGNOSTICS article inENGINE PERFORMANCE.


52/501

The Malfunction Indicator Lamp (MIL) request circuit signals the Powertrain Control Module (PCM) that thetransmission control module (TCM) is requesting MIL illumination.

Conditions For Running DTC

The engine is running.

Conditions For Setting DTC

The TCM is requesting MIL illumination, or that the MIL request circuit is shorted to ground.

Action Taken When DTC Sets

The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs andfails.

The control module records the operating conditions at the time the diagnostic fails. The control modulestores this information in the Freeze Frame/Failure Records.

Conditions For Clearing MIL/DTC

The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cyclesthat the diagnostic runs and does not fail.

A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any otheremission related diagnostic.

Clear the MIL and the DTC with a scan tool.

Test Description

The number below refers to the step number in the diagnostic procedures.

2- If the TCM has DTCs set that are requesting MIL illumination, those DTCs must be diagnosed first.

Diagnostic Procedures

1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, go toDIAGNOSTIC SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article in ENGINEPERFORMANCE.

2. Connect a scan tool. Are there any transmission DTCs set? If yes, go to next step. If no, go to step 5 .

3. Diagnose and repair any transmission DTCs. After repairs, go to next step.

4. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Startthe engine. Operate the vehicle within the Conditions for Running in the DTC or as close to the FreezeFrame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to nextstep. If no, go to INTERMITTENTS in appropriate FAULT ISOLATION article in ENGINEPERFORMANCE.


53/501

5. Disconnect the TCM. Connect a Digital Multimeter (DMM) from the MIL request circuit in the TCMharness connector to a good ground. Turn ON the ignition, with the engine OFF. Does the voltage

measure near battery voltage? If yes, go to step 7 . If no, go to next step.6. Test the MIL request circuit for a short to ground. Did you find and correct the condition? If yes, go to

step 9 . If no, go to step 8 .

7. Replace the TCM. After repairs, go to step 9 .

8. Replace the PCM. See POWERTRAIN CONTROL MODULEunder REMOVAL &INSTALLATION. Reprogram PCM. See PROGRAMMING in appropriate SELF-DIAGNOSTICSarticle in ENGINE PERFORMANCE. After repairs, go to next step.

9. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate thevehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. Ifno, go to step 2 .

10. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs thatyou have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriateSELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no, system is okay.

DTC P0701: TRANSMISSION CONTROL SYSTEM PERFORMANCE

Circuit Description

The Transmission Control Module (TCM) monitors the status of the pressure switches at start-up to detect thepresence of hydraulic pressure.




The components are powered, and ignition voltage is greater than 9 volts and less than 18 volts. Enginespeed is greater than 200 RPM and less than 7500 RPM for 5 seconds.


DTC will set under the following conditions:

Transmission fluid temperature is above -13F (-25C).


All pressure switches do not indicate pressure (at start-up).

Engine speed is above 500 RPM for 6 seconds or 400 RPM for 15 seconds.

Forward or Reverse gear is selected.



54/501



DTC will be stored in TCM history.

TCM inhibits TCC engagement.





Test Description

The number listed below refers to step number in the diagnostic procedure:

5- This step tests for line pressure.



2. Install the scan tool. Turn ignition on, engine off. Record the DTC failure records. Check the transmission

fluid level. See SERVICING - "C" & "K" SERIES (ALLISON)article. Is the transmission fluid levelcorrect? If so, go to next step. If not, go to step 4 .

3. This DTC can be set after performing fluid service and filter change, after replacement of the pressureswitch manifold, or after a long period of storage. Have any of these conditions occurred? If so, go to step7 . If not, go to step 5 .

4. Add fluid to the proper level. Is the fluid at the appropriate level? If so, go to next step.

5. Check the transmission line pressure. See HYDRAULIC PRESSURE TESTSunder PERFORMANCE

TESTS. Is the line pressure correct? If so, go to step 7 . If not, go to next step.6. No main line pressure at idle may be an indication of the following:

Stuck or sticking lube regulator valve.

Stuck or sticking line pressure regulator valve.

Loose or damaged suction filter.

Defective suction filter seal.

Was the reason for no line pressure condition found and repaired? If so, go to next step. If not, seeSYMPTOM DIAGNOSISunder TROUBLE SHOOTING.


Clear the DTC.


55/501

Operate the vehicle under normal driving conditions.

Did the DTC return? If so, go to step 1 . If not, system is okay.

Diagnostic Aids

DTC may set if a forward or reverse gear range is selected immediately after the engine is started and before theTCM detects pressure at the switches (2 to 6 seconds after engine start).

A plugged control main filter may cause this DTC to set. The control main filter is to be changed after the first

5000 miles. Failure to change the filter at this interval may cause this DTC and other pressure switch DTCs toset.

DTC P0703: BRAKE SWITCH CIRCUIT

Circuit Description

A mechanical switch attached to the brake pedal sends a signal to the Transmission Control Module (TCM)indicating the service brake has been applied. This signal is either ignition voltage or a ground signal dependingon the calibration installed in the TCM.



The components are powered, and ignition voltage is greater than 9 volts and less than 18 volts for a 12volt TCM.



DTC sets when the vehicle accelerates 10 times with the brake switch on, or decelerates 10 times with thebrake switch off.




Uses default assumption that brake is off.

TCM inhibits TCC engagement.


DTC ill l d h f ll i di i


56/501


A scan tool can clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up

cycles without failure.

Test Description


3- This step tests brake switch status.

4- This step tests for voltage at the TCM connector C1.

5- This step tests for voltage after the stoplamp switch.

6- This step tests for voltage before the stoplamp switch.



2. This DTC indicates that the TCM did not see the proper input signal for service brake status during anacceleration or deceleration cycle. This may indicate an open or short in the TCC brake switch/cruisecontrol release circuit or a faulty stoplamp switch. Go to next step.

3. Install the scan tool. Turn ignition on, engine off. Record the DTC failure record data. Apply and releasethe service brake. Does the scan tool indicate that the brake switch is toggling off and on? If so, seeDIAGNOSTIC AIDS. If not, go to next step.

4. Using DVOM, backprobe TCM connector C1 terminals No. 5 and 7. Apply and release the service brake.There should be no voltage reading at terminal No. 7 when the brake is applied. With the brake released,there should be 12 volts. Was voltage reading okay? If so, go to step 9 . If not, go to next step.

5. Using DVOM, probe stoplamp switch terminal "C" at the switch. Supply a ground connection at the otherlead. Apply and release the service brake. Is the switch turning voltage on and off? If so, go to step 7 . Ifnot, go to next step.

6. Measure voltage at stoplamp switch terminal "D". Is voltage available? If so, go to step 8 . If not, see

appropriate ANTI-LOCK article in BRAKES.

7. Repair the TCC brake switch/cruise control wiring harness. Is the repair complete? If so, go to step 10 .

8. Replace the stoplamp switch. See STOPLAMP SWIT

Documents

At Diagnosis