Automatic Transmission for Range Rover 4.6 HSE P68

1999 MODEL YEAR 4HP22EHAUTOMATIC TRANSMISSION

The automatic transmission used on DiscoverySeries II is the ZF4HP22EH electronically/hydraulically controlled 4 speed gearbox. This gearbox is similar in design mechanically to theautomatic transmission used in the pre 1999model year Range Rover.

The most significant difference between theautomatic transmissions used in pre 1999model year Discoverys and the automatictransmission used in Discovery Series II is theaddition of electronic transmission control. InDiscovery Series II, gear selection, gear changespeeds and torque converter lock up are now controlled electronically/hydraulically, ratherthan being controlled by mechanical/hydraulicmeans.

DISCOVERY SERIES II

634HP22EH Automatic Transmission

1 Transmission high/low switch2 Mode switch3 Gear position switch connector4 Solenoid valve/speed sensor connector5 Electronic automatic transmission ECU6 Engine control module

7 Diagnostic socket8 Instrument pack9 Transmission fluid temperature sensor10 Body control unit11 Battery power supply12 Ignition power supply

DISCOVERY SERIES II

Introduction to Land Rover Products - 1999/2000 MY Update64

1. Input/impeller 10. Epicyclic gear set2. Converter lock-up clutch 11. Clutch3. Turbine 12. Clutch brake4. Clutch forward drive 13. Input to transfer gearbox5. Clutch reverse drive 14. Freewheel (one way clutch)6. Clutch brake 15. Freewheel (one way clutch)7. Clutch brake 16. Freewheel (one way clutch8. Clutch brake 17. Stator and one way clutch9. Epicyclic gear set

There are a number of advantages provided byan automatic transmission equipped with anelectronically/hydraulically control system compared to an automatic transmission featuringa more conventional mechanically governedsystem. The main advantages are:

The gear change points of anelectronically/hydraulically controlledtransmission are more precise andconsistent. With mechanical/hydrauliccontrol there is a greater tolerance bandregarding the gear change points because ofthe nature of mechanical components, whichare influenced by conditions such astemperature and component wear.

The automatic transmission systemincorporates an output shaft speed sensorwhich is an input to the transmission controlmodule (TCM). The TCM selects the gearselectronically using solenoid valves. TheTCM determines which gear to select bymonitoring the signals received regardingroad speed, throttle angle, engine torque andengine speed.

The load on the transmission can be reducedby introducing engine intervention when theautomatic gearbox changes gear. Rather thanoperating independently of the enginemanagement system, the transmission TCMis capable of communicating with the enginecontrol module (ECM). In the case ofDiscovery Series II the ECM requests apercentage reduction of engine torque. Thisreduction results in an improvement in gearshift quality .

GEAR POSITION SWITCH

The gear position switch is mounted on the sideof the transmission and contains internalswitches. This switch has four input lines knownas the W, X, Y, and Z lines. The gear positionswitch provides the TCM with the currentdriver-selected gear position. By analyzing thestatus of these inputs, the TCM calculates whichgear is most suitable for the current conditions.

Range Rover has only three input lines from theposition switch: X, Y, and Z. Discovery Series II uses the fourth line for improved electricaldiagnostics and better lever position information(intermediate gear lever positions, i.e. to detectwhen the gear lever is moving betweenpositions). This helps to align mechanical andelectrical tolerances.

DISCOVERY SERIES II


ELECTRONIC CONTROL

The TCM is located under the left hand frontseat. Using information from the enginemanagement ECM, together with its ownsensors, the TCM selects the most suitable gear.

The gear is selected depends on certainvariables, including:

Road speed (from output shaft sensor)

Throttle angle (from engine management)

Engine Torque (from engine management)

Altitude (from engine management)

Selector position (from position switch)

Other factors such as vehicle acceleration arealso taken into account when the optimum gearis calculated.

The TCM controls gear selection by directingpressurized transmission fluid to the requiredclutch assembly. This is achieved by controllingthe operation of two shift solenoids incorporatedwithin the valve block.

The TCM controls the gear shift quality bymodulating the pressure regulator solenoid. Thissolenoid is incorporated into the automaticgearbox valve block.

To enhance the quality of the gear changes, theTCM sends a torque reduction signal to theECM during gear changes. Responding to thissignal, the engine management ECM will reduceengine torque to improve shift quality.

The third solenoid valve incorporated into thevalve block is the torque converter lock-upsolenoid. This solenoid is energized by the TCMwhen torque converter lock-up is required.

DISCOVERY SERIES II


HIGH RANGE

The high range gears should be used for allnormal driving, including off-road drivingacross dry level terrain.

NOTE: If the gear lever is moved from drive toa lower gear while the vehicle is moving atspeed, the selected gear will be engaged onlywhen the road speed is reduced to an acceptablelevel. This prevents the possibility of the enginefrom over-revving.

LOW RANGE

Low range gears should be selected in anysituation where low speed maneuvering isnecessary, extreme off-road condition driving isrequired or hill descent control (HDC) isrequired. Selection is made via the HI/LO leversituated on the vehicles center console.

TORQUE CONVERTER LOCK UP

At vehicle pull away and during gear changes,the torque converter will allow a certain amountof slip to occur between the crankshaft driveplate and the input shaft of the gearbox.Incorporated into the design of the automatictransmission system used on Discovery Series II is a lock-up feature, where the TCM willactivate the torque converter lock-up solenoid.Discovery Series II will lock the torqueconverter in all gears, whereas on pre 1999Range Rover this can only be activated in thirdand fourth gears. When activated, the torqueconverter lock-up clutch will be engaged and noslip will be allowed. Direct drive through thetorque converter will be provided in thiscondition.

The torque converter can be locked andunlocked during driving to improve driveability,fuel consumption and gear changing. The torqueconverter will not be locked until thetransmission has calculated that the oiltemperature has reached a predeterminedtemperature. This is calculated from the enginecoolant temperature via a software timer withinthe TCM, as the transmission itself has notemperature sensor. The length of this timerdepends on several variables, including theengine coolant temperature during cranking, butis approximately:

When low range is engaged, the torqueconverter is used to improve the vehiclesoff-road capabilities. One example of this islocking the torque converter at 0% throttle. Thisimproves engine braking while negotiating steepgradients. This feature will be active only whilethere is no danger of stalling the engine.

MODE SELECT

In addition to providing drive, and electronicallycontrolling the gear changes throughout theconventional gear selection range in both highand low ranges, the automatic transmissionsystem featured on Discovery Series II alsoincorporates a mode select facility. This featureenables the driver to select the gear changestrategy that most suits the current drivingconditions. The mode switch, situated adjacentto the rear of the automatic selector gate, can beused to select a Sport mode when in high range,and Manual mode when low range is selected.

DISCOVERY SERIES II


12 minutes-13F (-25C) 7 minutes32F (0C) 0 minutes77F (25C)

Time taken foroil to warm up

Engine ambienttemperature

Sport mode Sport mode can be selected by pressing themode button whenever high range is engaged.Once sport mode has been selected, a dashboard lamp will illuminate the letter S.Although automatic gear shifts continue to becontrolled by the TCM, they will be made usinga different strategy, i.e. remaining in a givengear longer when accelerating, and changingdown to a lower gear earlier when decelerating .The characteristics of the transmission while insport mode help make optimum use of theengines power. Pressing the mode button for asecond time returns the transmission system toits normal operation within the high range.

Manual mode Manual mode is selected by pressing the modebutton whenever low range is selected. Withmanual mode selected a dashboard lamp willilluminate the letter M. The transmission willfunction in a similar way to a manual gearbox.In this condition the transmission will changeinto the selected gear as soon as possible, andthen remain in that gear at all speeds, changingdown only to prevent engine stall. For example,if the selector position is in 3 while driving innormal modes, gears 1,2 and 3 will be availableHowever, in manual mode, if position 3 isselected, the transmission will select 3rd gearvery shortly after pulling away from rest.

This mode is designed to give improved off roadperformance, and kickdown is disabled in thismode.

Towing/steep gradientsWhen the vehicle is normal mode (i.e. highrange with sport not selected) the automaticgearbox will select a shift pattern appropriate tothe current conditions. If a heavy load is beingpulled, a steep gradient is being climbed or both,then the automatic gearbox will use a moreaggressive shift pattern, compensating for the

load by using higher engine speeds for any giventhrottle angle.

Compensation for reduced enginetorqueIn a similar way to the Towing mode, if thevehicle is producing less torque than wouldnormally be the case (high altitude or very hotair into the engine) then the transmission willhold onto gears longer than would normally bethe case. This is a very similar situation totowing, but the performance of the vehicle isreduced due to a lack of engine power, ratherthan the weight of the vehicle.

Calibration Selection (99MY V8 RangeRover Only)North American ECU part numbers are differentfrom UK/Euro, and Rest of world. Each ECUcontains two calibrations, 4.0l and 4.6l. Whenan ECU is installed in a vehicle, the correctcalibration must be selected, or a gearbox faultwill be stored, and Gearbox fault will bedisplayed in the message centre. The vehicle canbe driven in this state, and is not in limp homemode. However, vehicles must not be driven forlong in this condition.

When the correct calibration is selected (4.0 or4.6), the fault code memory is deletedautomatically. If the ECU is removed from thevehicle, the correct calibration is remembered.For this reason, it is important that if ECUs areswapped between vehicles, the correctcalibration must be selected.

DISCOVERY SERIES II


FAULT FINDING DIAGNOSTICS

If there is a fault, the automatic transmissionwill attempt to drive as normally as possible.However, if it is not safe to continue changinggear, a limp home mode will be selected.

Limp home mode differs depending upon thevehicle conditions when the fault is diagnosed.If high range is selected, then the defaultcondition is third, if stationary when the faultoccurred and fourth, (if moving) when the faultoccurred. If low range is selected, then thesystem will attempt to maintain the current gearuntil the ignition supply is removed. This is incase the fault occurs while negotiating a steepgradient.

If there is a fault which either prevents all gearsbeing used or disables the kick-down facility,the sport and manual lights will flash at thesame time. This indicates to the driver that thevehicle has entered limp home mode. This modewill continue until the ignition is turned off.When the ignition is turned back on and theengine has been cranked, the TCM willcomplete a self-test. If the fault has rectifieditself the automatic gearbox will resume normaloperation and the sport and manual lights willno longer flash. If the fault is still evident, thenthe vehicle should be taken to the nearest LandRover dealer as soon as possible for the fault tobe investigated and rectified. It is important toappreciate that if a fault has been rectified or isno longer present but the fault code has not beendeleted, the sport and manual lights willcontinue to flash until the TCM has diagnosedthe fault is no longer present.

If a fault exists that will not damage thetransmission or cause inconvenience to thedriver, no warning lights will illuminate but afault code will be stored. If a driver does noticea slight change with the behavior of the gearbox,this could be due to a fault of this type.

If a transmission fault exists that will increasethe emissions of the vehicle, the malfunctionindicator lamp (MIL) will illuminate.

If any of the above conditions are true, thesoftware within the transmission TCM will havestored a fault code. After a fault code has beenstored and the car has completed 40 warm-ups,(Warm-up is defined as the engine coolant risingby at least 61F (16C) and exceeding 158F(70C)), then the vehicle fault code will bedeleted from memory providing the fault doesnot reappear during this time. If the fault codesreappear, this counter is reset and requiresanother 40 warm-ups before the fault is deletedautomatically.

If the automatic transmission TCM is found tohave been disconnected, the vehicle will haveselected an hydraulic limp home mode.Reconnection must occur when the ignition isswitched off. If the TCM was disconnectedwhile the ignition was turned on, fault codeswill have been stored within the ECM andTCM. These fault codes must be deleted usingTestBook.

ENGINE MANAGEMENT FAULTS

Faults can occur with the engine managementsystem which affect the transmissionsperformance. After the fault has been diagnosedthrough interrogating the ECM, and has beenrectified successfully, the fault must be clearedfrom the ECM and TCM using TestBook. OnV-8 derivatives, if a fault has been stored in theTCM, it will illuminate the MIL (service enginelamp). This will happen only if the fault isemissions-related i.e. torque converter notfunctioning or 3rd/ 4th gear permanentlyselected.

DISCOVERY SERIES II


ON BOARD DIAGNOSTIC (OBD) SYSTEM

The TCM communicates with the ECM via aCAN interface. This is used by the transmissionfor the gearshift torque interface and as a meansfor transmitting OBD information between theTCM and ECM. The automatic transmissionrequests the ECM that freeze frame data isstored, and requests MIL activation. If the MILis illuminated without any fault codes beingstored in the ECM, then the automatictransmission is requesting MIL activation. Theautomatic transmission MIL activation requestcan be checked with TestBook.

CAN SYSTEM

The controller area network (CAN) is a highspeed serial interface for transmittinginformation between control modules. CANcommunications are self checked for errorsand if an error is detected, the message isignored by the receiving control module. Due tothe high rate of information exchange, thesystem has a high degree of latency (at resttime, waiting for information to process). Thisallows for an error to be present withoutreducing the overall data transfer rate.

DISCOVERY SERIES II


OnOffMaintains current gear in low range, limphome mode in range. Shift pressure tomaximum, harsh gear shifts/engagement.

* Battery supply below 9Vwhile engine running

P1562 (24)

OnOnLimp home mode in low and high ranges.Shift pressure to maximum, harsh gear shifts/engagement.

* Shift solenoid (MV 2),open or short circuit

P0758 (9, 27)


* Shift solenoid (MV 1),open or short circuit

P0753 (8, 26)

OnOnLimp home mode in low and high ranges.Shift pressure to maximum, harsh gear shifts/engagement

* Pressure regulatingsolenoid (MV 4), open orshort circuit

P0748 (10, 28)

OnOnLimp home mode in low and high ranges.Shift pressure to maximum, harsh gear shifts/engagement

* Torque converter lock-upsolenoid (MV 3), open orshort circuit

P0743 (7, 25)

OffOnMay affect driveability.* Torque converter lock-upclutch fault

P0741 (5)

OffOnNo apparent effect* Ratio monitoring,implausible 4th gear ratio

P0734 (32)

OffOnNo apparent effect* Ratio monitoring,implausible 3rd gear ratio

P0733 (31)

OffOnNo apparent effect* Ratio monitoring,implausible 2nd gear ratio

P0732 (30)

OnOnNo apparent effect* Ratio monitoring,implausible 1st gear ratio

P0731 (29)

OnOnMaintains current gear in low range, limphome mode in high range. Shift pressure tomaximum, harsh gear shifts/engagement.

* Torque converter slippingP0722 (22)


* Downshift safety monitorprevented downshift whichwould have caused engineoverspeed

P0721 (21)

OnOnMaintains current gear in low range, limphome mode in high range. Shift pressure tomaximum, harsh gear shifts/engagement

* Gear position switch,incorrect outputs

P0705 (14, 23)

Sport/Manual

MIL

Warning lampillumination

EffectFault description

Fault code,OBD II

(TestBook)

DISCOVERY SERIES II


* = Emissions (OBD II) relevantOn = MIL illuminates immediately (in all other faults, MIL On = illuminates in the 2nd consecutive drive cycle iffault still present)

OffOnNo reduced torque compensation, possiblereduction in performance/ driveability ataltitude or high ambient temperatures.

Altitude shift control invalidP1844 (38)

OffOnNo apparent effect.CAN message: Engine airintake temperature invalid

P1884 (37)


* CAN message: Engine speed invalid

P1884 (35)

OffOnSubstitute engine torque of derived from other

inputs. May affect shift quality.

* CAN message: Engine torque invalid

P1884 (33, 34)

OffOnNo apparent effect.CAN message: Road speed invalid

P1884 (20)

OffOnSubstitute engine temperature derived fromother inputs. No apparent effect.

CAN message: Enginetemperature invalid

P1884 (19)

OnOnSubstitute throttle angle of 50% adopted. Nokickdown. Operates in economy modes only.

* CAN message: Throttle position invalid

P1884 (18)

OffOnNo apparent effect.* CAN message: Engine friction invalid

P1884 (11)


* CAN time-out monitoring

P1843 (17)


* CAN level monitoringP1842 (15)


* CAN bus faultP1841 (16)

OffOnLamp fails bulb check or is permanentlyilluminated. No effect on gearbox operation.

Sport/Manual warninglamp circuit fault

P1810 (12, 13)

OffOnNo apparent effectTransmission high/lowrange, implausible input

P1705 (39)


* Solenoid valves powersupply relay, sticking openor short circuit

P1613 (1)


* Solenoid valves powersupply relay, stickingclosed or open circuit

P1612 (2)

OnOnNo apparent effect* Watchdog P1606 (6)

OffOnNo apparent effect* EEPROMP1606 (3)


* ECU, EEPROM checksumP1601 (4)

Sport/Manual

MIL

Warning lampillumination

EffectFault description

Fault code,OBD II

(TestBook)

SERVICE MAINTENANCE

The automatic transmission identificationnumber can be found stamped on a plate rivetedto the bottom left hand side of the autotransmission casing.

There is no filler/dipstick tube used on theautomatic transmission. Discovery Series II uses a filler plug and a drain plug for servicemaintenance of the transmission fluid.

The procedure for the automatic gearbox drainand refill is as follows:

Drain

1. Position vehicle on ramp.

2. Apply handbrake and position chocks underfront and rear wheels.

3. Position container under gearbox.

4. Remove gearbox drain plug and allow oil todrain, discard sealing washer.

5. Refit drain plug using new sealing washer andtighten to 15Nm (11Ibf. ft).

Refill1. Remove filler/level plug and discard sealing

washer.

2. Refill gearbox to bottom of filler/level plughole with correct grade of fluid.

3. Ensure gear lever is in the P position, startengine and move selector lever through allgear positions and back to P position.

4. With the engine idling, continue fillinggearbox until a small thread of fluid runsfrom filler/level orifice.

5. Refit filler / level plug using a new sealingwasher and tighten to 22Ibs/ft (30 Nm).

The scheduled service requirement for theautomatic gearbox, relates to the maintenance ofthe transmission oil and automatic gearbox oilfilter. The oil specified for use is ATF DexronIID OR III from the approved list. The fluidcapacity is 10.25 quarts (9.7 liters) dry fill, refillquantity being dependent upon oil temperatureat time of draining and length of time allowed todrain.

Always refer to the current maintenance sheetwhenever servicing Discovery Series II , toensure the correct schedule is always followed.

DISCOVERY SERIES II


Documents

Automatic Transmission for Range Rover 4.6 HSE P68