95ZJ_25.PDF

EMISSION CONTROL SYSTEMS

CONTENTS

page page

COMPONENT REMOVAL/INSTALLATION . . . . . . 15EVAPORATIVE EMISSION CONTROLS . . . . . . . . 5

EXHAUST EMISSION CONTROLS . . . . . . . . . . . 11GENERAL INFORMATION . . . . . . . . . . . . . . . . . . 1

GENERAL INFORMATION

INDEX

page page

DRB Scan Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4On-Board Diagnostics . . . . . . . . . . . . . . . . . . . . . . . 1

Vacuum Hose Routing Schematics . . . . . . . . . . . . . 1Vehicle Emission Control Information (VECI) Label . 1

VEHICLE EMISSION CONTROL INFORMATION(VECI) LABEL

All vehicles are equipped with a combined VECI la-bel. The label is located in the engine compartment(Fig. 1). The label contains the following:• Engine family and displacement• Evaporative family• Emission control system schematic• Certification application• Engine timing specifications (if adjustable)• Idle speeds (if adjustable)• Spark plug and plug gap

The label also contains an engine vacuum sche-matic. There are unique labels for vehicles built forsale in the state of California and the country ofCanada. Canadian labels are written in both the En-

glish and French languages. These labels are perma-nently attached and cannot be removed withoutdefacing information and destroying label.

The VECI label illustration (Fig. 2) is used asan example only. Refer to the VECI label located inthe engine compartment (Fig. 1) for actual emissioninformation.

VACUUM HOSE ROUTING SCHEMATICSThe vacuum hose routing schematics are used

as examples only. If there are any differences be-tween these schematics and the Vehicle EmissionControl Information (VECI) label schematics, thoseshown on the VECI label should be used.

ON-BOARD DIAGNOSTICS

FOR CERTAIN EMISSION SYSTEMCOMPONENTS

The powertrain control module (PCM) performs anOn-Board Diagnostic (OBD) check for certain emis-sion system components on all vehicles. This is doneby setting a diagnostic trouble code (DTC).

A DTC can be obtained in two different ways. Oneof the ways is by connecting the DRB scan tool to thedata link connector. This connector is located in theengine compartment (Fig. 3). Refer to the appropriatePowertrain Diagnostic Procedures service manual foroperation of the DRB scan tool. The other way is tocycle the ignition key and observe the malfunction in-dicator lamp (MIL). The MIL lamp is displayed onthe instrument panel as the CHECK ENGINE lamp(Fig. 4). This lamp will flash a numeric code. If a nu-meric code number 32 is observed, a problem has

Fig. 1 VECI Label Location—Typical

ZJ EMISSION CONTROL SYSTEMS 25 - 1

been found in the EGR system. If a numeric codenumber 31 is observed, a problem has been found inthe EVAP system.

EGR System Check: The OBD check will activateonly during selected engine/driving conditions. Whenthe conditions are met, the PCM energizes the EGRvalve control solenoid to disable the EGR. The PCMchecks for a change in the oxygen sensor signal. Ifthe air-fuel mixture goes lean, the PCM will attemptto enrichen the mixture. The PCM registers a diag-nostic trouble code (DTC) if the EGR system hasfailed or degraded. After registering a DTC, the PCMturns the CHECK ENGINE lamp on. Illumination ofthis lamp indicates the need for immediate service.Note that the CHECK ENGINE lamp will illuminate

initially for approximately two seconds each time theignition key is turned to the ON position. This isdone for a bulb test.

For a complete operational description of allDTC’s, for accessing a DTC and for erasing aDTC, refer to On-Board Diagnostics. This canbe found in the General Diagnosis sections ofGroup 14, Fuel System. For numeric flash lampcode charts for emission related components,refer to Diagnostic Trouble Code (DTC). Thiscan also be found in the General Diagnosis sec-tions of Group 14, Fuel System.

VACUUM ROUTING SCHEMATIC—NON-CALIFORNIA 4.0L ENGINE—TYPICAL

Fig. 2 VECI Label—Typical

25 - 2 EMISSION CONTROL SYSTEMS ZJ

VACUUM ROUTING SCHEMATIC—CALIFORNIA 4.0L ENGINE—TYPICAL

VACUUM ROUTING SCHEMATIC—5.2L V-8 ENGINE—TYPICAL


DRB SCAN TOOLFor operation of the DRB scan tool, refer to the ap-

propriate Powertrain Diagnostic Procedures servicemanual.

Fig. 4 Check Engine Lamp Location

Fig. 3 Data Link Connector—Typical


EVAPORATIVE EMISSION CONTROLS

INDEX

page page

Crankcase Breather/Filter—5.2L Engines . . . . . . . . 10Crankcase Ventilation System—4.0L 6-Cylinder

Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7EVAP (Evaporation) Control System . . . . . . . . . . . . 5

Fuel Tank Filler Tube Cap . . . . . . . . . . . . . . . . . . . . 7Positive Crankcase Ventilation System—5.2L V-8

Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Pressure Relief/Rollover Valve . . . . . . . . . . . . . . . . 10

EVAP (EVAPORATION) CONTROL SYSTEM

GENERAL INFORMATIONThe function of the EVAP control system is to pre-

vent the emissions of gasoline vapors from the fueltank into the atmosphere. When fuel evaporates inthe fuel tank, the vapors pass through vent hoses ortubes to a carbon filled EVAP canister. They are tem-porarily held in the canister until they can be drawninto the intake manifold when the engine is running.

The EVAP canister is a feature on all models forthe storage of fuel vapors from the fuel tank. Refer tothe following EVAP Canister for information.

Three different EVAP systems are used. These arefor:• The 4.0L six-cylinder engine without the Califor-nia emission package.• The 4.0L six-cylinder engine with the Californiaemission package.• The 5.2L V-8 engine.

Refer to the following System Operation sectionsfor information.

The hoses used in this system are speciallymanufactured. If replacement becomes neces-sary, it is important to use only fuel resistanthose.

EVAP CANISTERA sealed, maintenance free, EVAP canister is used

on all vehicles. Depending on engine and emissionpackages, two different types of canisters are used.The EVAP canister is located in the left front cornerof the vehicle below the left front headlamp (Figs. 1or 2). The canister is filled with granules of an acti-vated carbon mixture. Fuel vapors entering the can-ister are absorbed by the charcoal granules.

A separate EVAP canister filter is used on 4.0L6-cylinder engines equipped with the CaliforniaEmission Package only. This filter is located in theleft front corner of the engine compartment behindthe air cleaner housing. On the 5.2L V-8 engine, thisfilter is located at the end of the vacuum line harnesswhere the connection is made at the EVAP purge so-lenoid. On the 4.0L engine without the Californiapackage, the engine air cleaner housing is used.

SYSTEM OPERATION

4.0L ENGINE WITHOUT CALIFORNIA EMISSION PACKAGEThis is a non-electrical, vacuum operated system.The EVAP canister is equipped with a vacuum con-

trolled purge shutoff switch (orifice) (Fig. 3) that con-trols canister purge operation. The switch is openwhen engine manifold vacuum is applied to it. Whenthe engine is operating, the EVAP canister purgefunction draws fresh air through the top of the can-ister. This causes the stored vapors to be drawn outof the canister and into the airstream in the aircleaner housing snorkel (Fig. 3).

The air cleaner contains a venturi in the aircleaner cover used as a purge line vacuum source(Fig. 4). The venturi effect increases the speed of theintake air flowing by the slots in the venturi wall.This creates a low pressure area around the slots.When the purge shutoff switch is open, vapors fromthe canister are drawn through slots and into the air-stream flowing through the venturi (Fig. 4).

The fuel vapors then pass through the intake man-ifold and into the engine combustion chambers. Herethey are consumed during engine combustion.

Fig. 1 Canister Location—All Engines—Non-California


SYSTEM OPERATION

4.0L ENGINE WITH CALIFORNIA EMISSION PACKAGEThis is a combination electrical and vacuum oper-

ated system.The duty cycle EVAP canister purge solenoid (Fig.

5) regulates the rate of vapor flow from the EVAPcanister to the intake manifold. The powertrain con-

trol module (PCM) operates the purge solenoid bycontrolling the ground circuit to it.

During the cold start warm-up period and the hotstart time delay, the PCM does not energize the sole-noid. When de-energized (pulse ground signal notsupplied), no vapors are purged.

The engine enters closed loop operation after itreaches a specified temperature and the programmedtime delay ends. During closed loop operation, the

Fig. 2 Canister Location—California EmissionPackage—4.0L Only

Fig. 3 EVAP System—Non-California 4.0L Engine—Typical

Fig. 4 Air Cleaner Venturi—Non-California 4.0LEngine—Typical

Fig. 5 Purge Solenoid—4.0L Engine—CaliforniaEmission Package


PCM energizes and de-energizes the solenoid 5 to 10times per second, depending upon operating condi-tions. The PCM varies the vapor flow rate by chang-ing the solenoid pulse width. Pulse width is theamount of time the solenoid is energized.

As the solenoid is energized, the fuel vapors thenpass through the intake manifold and into the enginecombustion chambers. Here they are consumed dur-ing engine combustion.

SYSTEM OPERATION

5.2L V-8 ENGINEThis is a combination electrical and vacuum oper-

ated system.Fuel tank pressure vents into the EVAP canister.

Fuel vapors are temporarily held in the canister untilthey can be drawn into the intake manifold. TheEVAP canister purge solenoid allows the EVAP can-ister to be purged at predetermined times and at cer-tain engine operating conditions.

Vacuum for the EVAP canister is controlled by theEVAP canister purge solenoid (Fig. 6). The solenoid isoperated by the powertrain control module (PCM).The PCM regulates the solenoid by switching theground circuit on and off based on engine operatingconditions. When energized (grounded), the solenoidprevents vacuum from reaching the EVAP canister.When not energized, the solenoid allows vacuum toflow through to the EVAP canister.

During warm-up and for a specified time period af-ter hot starts, the PCM grounds the EVAP canisterpurge solenoid causing it to energize. This will pre-vent vacuum from reaching the EVAP canister valve.When the engine reaches an operating temperatureof approximately 60°C (140°F), the PCM removes theground to the solenoid. The de-energized solenoidthen allows vacuum to flow to the EVAP canister andpurge fuel vapors through the intake manifold and

into the engine combustion chambers. Here they areconsumed during engine combustion.

The EVAP canister purge solenoid will also be en-ergized during certain idle conditions in order to up-date the fuel delivery calibration.

FUEL TANK FILLER TUBE CAPThe fuel tank filler tube cap (fuel tank cap) incor-

porates a two-way relief valve that is closed to atmo-sphere during normal operating conditions. The reliefvalve used in fuel filler caps of all models is cali-brated at a pressure of 10 kPa (1.5 psi) or a vacuumof 6 kPa (1.8 in. Hg). When the pressure or vacuumis relieved, the valve returns to the normally closedposition.

CAUTION: The fuel filler cap must be removed priorto disconnecting any fuel system component.

CRANKCASE VENTILATION SYSTEM—4.0L6-CYLINDER ENGINE

The 4.0L engine is equipped with a Crankcase Ven-tilation (CCV) system (Fig. 7). The CCV system per-forms the same function as a conventional PCVsystem, but does not use a vacuum controlled valve.

A molded vacuum tube connects manifold vacuumto top of cylinder head cover at dash panel end. Thevacuum tube contains a fixed orifice (Fig. 7) of a cal-ibrated size. It meters the amount of crankcase va-pors drawn out of the engine.

A fresh air supply hose from the air cleaner (Fig. 7)is connected to front of cylinder head (valve) cover.When the engine is operating, fresh air enters theengine and mixes with crankcase vapors. Manifoldvacuum draws the vapor/air mixture through thefixed orifice and into the intake manifold. The vaporsare then consumed during engine combustion.

POSITIVE CRANKCASE VENTILATION SYSTEM—5.2L V-8 ENGINE

DESCRIPTION/OPERATIONThe 5.2L V-8 engine is equipped with a closed pos-

itive crankcase ventilation (PCV) system (Fig. 8).This system consists of a crankcase PCV valve

mounted on the cylinder head cover with a hose ex-tending from the valve to the intake manifold.

A closed engine crankcase breather/filter, with ahose connecting it to the air cleaner housing, pro-vides the source of air for system.

The positive crankcase ventilation (PCV) systemoperates by engine intake manifold vacuum (Fig. 9).Filtered air is routed into the crankcase through theair cleaner hose and crankcase breather/filter. Thisforces crankcase vapors through the PCV valve. It isthen drawn into the intake manifold. Here it be-comes part of the calibrated air/fuel mixture to be

Fig. 6 Purge Solenoid—5.2L Engine—Typical


consumed in the combustion chamber. The PCV sys-tem constantly ventilates the crankcase to help pre-vent sludge formation and vapors from entering theatmosphere.

POSITIVE CRANKCASE VENTILATION (PCV)VALVE

The PCV valve contains a spring loaded plunger.This plunger meters the amount of crankcase vaporsrouted into the combustion chamber based on intakemanifold vacuum.

When the engine is not operating, or during an en-gine popback, the spring forces the plunger backagainst the seat. This will prevent vapors from flow-ing through the valve (Fig. 10).

Fig. 8 PCV Valve/Hose—5.2L Engines Fig. 9 Typical Closed Crankcase Ventilation System

Fig. 7 CCV System—4.0L Engine—Non-California System Shown


During periods of high manifold vacuum, such asidle or cruising speeds, vacuum is sufficient to com-pletely compress spring. It will then pull the plungerto the top of the valve (Fig. 11). In this position thereis minimal vapor flow through the valve.

During periods of moderate manifold vacuum, theplunger is only pulled part way back from inlet. Thisresults in maximum vapor flow through the valve(Fig. 12).

INSPECTION AND SERVICE PROCEDURE(1) With engine idling, remove the PCV valve from

cylinder head cover. If the valve is not plugged, ahissing noise will be heard as air passes through thevalve. Also, a strong vacuum should be felt at thevalve inlet (Fig. 13).

(2) Install the PCV valve. Remove the crankcasebreather/filter. Hold a piece of stiff paper, such as aparts tag, loosely over the opening of crankcasebreather/filter at the cylinder head (valve) cover (Fig.14).

(3) The paper should be drawn against the openingin the cylinder head (valve) cover with noticeable

force. This will be after allowing approximately oneminute for crankcase pressure to reduce.

(4) Turn engine off and remove PCV valve fromcylinder head (valve) cover. The valve should rattlewhen shaken (Fig. 15).

Replace the PCV valve and retest the system if itdoes not operate as described in the preceding tests.Do not attempt to clean the old PCV valve.

(5) If the paper is not held against the opening incylinder head (valve) cover after new valve is in-stalled, the PCV valve hose may be restricted andmust be replaced. The passage in the intake manifoldmust also be checked and cleaned.

(6) To clean the intake manifold fitting, turn a 1/4inch drill (by hand) through the fitting to dislodge

Fig. 10 Engine Off or Engine PopBack—No VaporFlow

Fig. 11 High Intake Manifold Vacuum—MinimalVapor Flow

Fig. 12 Moderate Intake Manifold Vacuum—Maximum Vapor Flow

Fig. 13 Check Vacuum at PCV Valve—Typical

Fig. 14 Check Vacuum at Crankcase BreatherOpening—Typical


any solid particles. Blow out the fitting with shop air.If necessary, use a smaller drill to avoid removingany metal from the fitting.

CRANKCASE BREATHER/FILTER—5.2L ENGINESThe crankcase breather/filter is used with the 5.2L

V-8 engine only.The crankcase breather/filter (Fig. 16) is located on

the engine valve cover. It must be kept clean and lu-bricated. At the recommended interval, remove thefilter and wash it thoroughly in kerosene, or similarsolvent. Lubricate or wet the filter by inverting itand filling with SAE 30 engine oil. Filter must thenbe thoroughly drained. More frequent service may benecessary for vehicles operated extensively on shortrun, stop and go, or extended engine idle service.

The filter must be replaced at correct intervals. Re-fer to Lubrication and Maintenance, Group 0.

PRESSURE RELIEF/ROLLOVER VALVEThese vehicles are equipped with a combination

fuel tank pressure relief and rollover valve (Fig. 17).This dual function valve will relieve fuel tank pres-sure and also prevent fuel flow through the fuel tankvent hoses in the event of an accidental vehicle roll-over.

The valve incorporates a pressure relief mechanism(Fig. 18) that releases fuel tank pressure when thepressure increases above the calibrated sealing value.Refer to the Fuel Tank section of Group 14, Fuel Sys-tems for removal and installation procedures.

Fig. 15 Shake PCV Valve—Typical Fig. 16 Typical Crankcase Breather/Filter—5.2LEngine

Fig. 17 Pressure Relief/Rollover Valve Location

Fig. 18 Pressure Relief/Rollover Valve Operation


EXHAUST EMISSION CONTROLS

INDEX

page page

Catalytic Converter . . . . . . . . . . . . . . . . . . . . . . . . 11EGR (Exhaust Gas Recirculation) System—5.2L

Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Oxygen (O2S) Sensor . . . . . . . . . . . . . . . . . . . . . . 14

CATALYTIC CONVERTERRefer to Group 11, Exhaust System and Intake

manifold for information.

EGR (EXHAUST GAS RECIRCULATION) SYSTEM—5.2L ENGINE

GENERAL INFORMATIONThe Exhaust Gas Recirculation (EGR) System is

used with the 5.2L V-8 engine only.The EGR system reduces oxides of nitrogen (NOx)

in the engine exhaust and helps prevent sparkknock. This is accomplished by allowing a predeter-mined amount of hot exhaust gas to recirculate anddilute the incoming fuel/air mixture. This dilution re-duces peak flame temperature during combustion.

A malfunctioning EGR system can cause enginespark knock, sags or hesitation, rough idle, enginestalling and poor driveability.

EGR SYSTEM OPERATIONThe system consists of:

• An EGR valve assembly (Figs. 1 or 2) mounted tothe intake manifold.• An EGR valve control containing a combinationback-pressure transducer and an electric vacuum so-lenoid (Figs. 1 and 2).• The powertrain control module (PCM) to controlthe electric solenoid portion of the valve control.• An EGR tube (Fig. 3) connecting a passage in theintake manifold (near the EGR valve) to the rear ofthe right exhaust manifold.• Hoses to connect the various components.

When the PCM removes the ground signal to theelectric solenoid portion of the valve control, EGRsystem operation starts to occur. The PCM will mon-itor and determine when to supply and remove thisground signal depending on certain engine tempera-tures, throttle positions and other engine operatingconditions.

If the electrical connector to the EGR valvecontrol (solenoid) is disconnected, or the elec-trical signal is lost, the EGR valve will operateat all times. This may result in; poor engine perfor-mance, rough idle speed and reduced driveabilityduring certain operating conditions.

The EGR valve control also contains an internalpressure-type transducer (Fig. 2). This transducerportion of the valve control is operated by exhaustback-pressure from the EGR valve. Exhaust is deliv-ered to the EGR valve through the metal EGR tube(Fig. 3). This connects it to the rear of the right ex-haust manifold. A rubber hose connects the back-pressure fitting on the EGR valve to the back-pressure fitting on the valve control (Fig. 2).

When the ground signal is removed from the elec-tric portion of the valve control (solenoid is not ener-gized), and exhaust gas back-pressure entering theEGR valve inlet is high enough, back-pressure is sup-plied to the valve control. It then holds the bleedvalve in the transducer closed. This allows enginevacuum to flow through the EGR valve control to ac-tivate and operate the EGR valve for exhaust gas re-circulation. If back-pressure is not strong enough toclose the bleed valve in the transducer, the valve con-trol will bleed off engine vacuum preventing EGRvalve operation.

The transducer measures and uses this exhaustback-pressure signal from the EGR valve to regulate

Fig. 1 EGR System Component Location


and provide the correct amount of exhaust gas recir-culation under all conditions.

Exhaust gas recirculation will begin in this orderwhen:

• The powertrain control module (PCM) determinesthat EGR system operation is necessary.• The electrical portion of the EGR valve control isnot energized (grounded) by the PCM.• Exhaust back-pressure entering the transducer inthe EGR valve control is strong enough to close itsbleed valve.• Engine vacuum is passed through the EGR valvecontrol to the EGR valve.• The inlet seat (poppet valve) at the bottom of theEGR valve opens to dilute and recirculate exhaustgas back into the intake manifold.

For more information, also refer to Open Loop/Closed Loop Modes of Operation in Group 14, FuelSystems.

EGR GAS FLOW TESTUse the following test procedure to determine if ex-

haust gas is flowing through the EGR valve. It canalso be used to determine if the EGR tube is plugged,or the system passages in the intake or exhaust man-ifolds are plugged.

This is not to be used as a complete test of theEGR system.

The engine must be started, running and warmedto operating temperature for this test.

(1) All engines are equipped with two fittings lo-cated on the EGR valve (Fig. 4). The upper fitting(located on the vacuum motor) supplies engine vac-uum to a diaphragm within the EGR valve for valveoperation. The lower fitting (located on the base ofthe EGR valve) is used to supply exhaust back-pres-sure to the EGR valve control.

Fig. 2 EGR Valve and EGR Valve Control

Fig. 3 EGR Tube

Fig. 4 Typical EGR Valve


(2) Disconnect the rubber hose at the vacuum mo-tor fitting (Fig. 4) on the top of the EGR valve vac-uum motor.

(3) Connect a hand-held vacuum pump to this fit-ting.

(4) Start the engine.(5) Slowly apply 5 inches of vacuum to the fitting

on the EGR valve motor.(6) While applying vacuum, and with the engine

running at idle speed, the idle speed should drop orthe engine may even stall. This is indicating that ex-haust gas is flowing through the EGR tube betweenthe intake and exhaust manifolds.

(7) If the engine speed did not change, the EGRvalve may be defective, the EGR tube may beplugged with carbon, or the passages in the intakeand exhaust manifolds may be plugged with carbon.

(a) Remove EGR valve from engine. Refer toEGR Valve Removal in this group.

(b) Apply vacuum to the vacuum motor fittingand observe the stem on the EGR valve. If thestem is moving, it can be assumed that the EGRvalve is functioning correctly. The problem is in ei-ther a plugged EGR tube or plugged passages atthe intake or exhaust manifolds. Refer to step (c).If the stem will not move, replace the EGR valve.Note: The EGR valve, valve control and attachinghoses are serviced as one unit. Refer to EGR ValveRemoval/Installation in this group.

(c) Remove the EGR tube between the intakeand exhaust manifolds. Check and clean the EGRtube and its related openings on the manifolds. Re-fer to EGR Tube in this group for procedures.Do not attempt to clean the EGR valve. If the valve

shows evidence of heavy carbon build-up near thebase, replace it.

EGR SYSTEM TEST

WARNING: APPLY PARKING BRAKE AND/ORBLOCK WHEELS BEFORE TESTING THE EGR SYS-TEM.

(1) Warm up the engine and bring to operatingtemperature before performing the proceeding tests.

(2) Check the condition of all EGR system hosesand tubes for leaks, cracks, kinks and hardening ofrubber hoses. Repair and correct these conditions be-fore performing any tests.

(3) Be sure the hoses at both the EGR valve andEGR valve control are connected to the proper fit-tings. Refer to figure 2.

(4) Be sure the electrical connector is firmly con-nected at the valve control.

(5) To check EGR system operation, connect theDRB scan tool to the data link connector. The datalink connector is located in the engine compartment(Fig. 5). Refer to the appropriate Powertrain Diag-

nostic Procedures service manual for operation of theDRB scan tool when diagnosing the EGR system.

(6) After checking the system with the DRB scantool, proceed to the following: EGR Valve LeakageTest, or EGR Valve Control Test and repair as neces-sary.

EGR VALVE LEAKAGE TESTThis is not to be used as a complete test of the

EGR system.If the engine will not idle, dies out on idle, or idle

is rough or slow, the poppet valve (Fig. 2) at the baseof the EGR valve may be leaking in the closed posi-tion. The diaphragm (Fig. 2) within the EGR valvemay also be ruptured.

(1) The engine should be off for the following test.(2) Disconnect the rubber hose from the fitting

(Fig. 2) at the top (vacuum motor) side of the EGRvalve.

(a) Connect a hand-held vacuum pump to thisfitting.

(b) Apply 15 inches of vacuum to the pump.(c) Observe the gauge reading on the pump.(d) If vacuum falls off, the diaphragm in the

EGR valve has ruptured.(e) Replace the EGR valve. Note: The EGR valve,

valve control and attaching hoses are serviced asone unit. Refer to EGR Valve Removal/Installationin this group.

(f) If vacuum did not fall off, proceed to the nextstep.(3) A small metal fitting (back-pressure fitting) is

located at the base of the EGR valve (Fig. 2). A rub-ber back-pressure hose connects it to the back-pres-

Fig. 5 Data Link Connector—Typical Location


sure fitting on the EGR valve control. Disconnect thisrubber hose at the EGR valve fitting.

(4) Remove the air intake tube at the throttle body.(5) Using compressed air, and using an air nozzle

with a rubber tip, apply approximately 50 psi of reg-ulated shop air to the metal back-pressure fitting onthe EGR valve.

(6) By hand, open the throttle to the wide open po-sition. Air should not be heard emitting from theintake manifold while applying air pressure at theback-pressure fitting.

(7) If air can be heard emitting from the intakemanifold, the poppet valve (Fig. 2) is leaking at thebottom of the EGR valve. Replace the EGR valve.Note: The EGR valve, valve control and attachinghoses are serviced as one unit. Refer to EGR ValveRemoval/Installation in this group. Do not attemptclean the old EGR valve.

EGR VALVE CONTROL TEST

TESTING ELECTRICAL SOLENOID PORTION OF VALVECONTROL

This is not to be used as a complete test of theEGR system.

Electrical operation of the valve control should bechecked with the DRB scan tool. Refer to the appro-priate Powertrain Diagnostic Procedures servicemanual for operation of the DRB scan tool. Replacesolenoid (valve control) if necessary.

TESTING VACUUM TRANSDUCER PORTION OF VALVECONTROL

The first part of this test will determine if thetransducer diaphragm at the back-pressure side ofthe valve control has ruptured or is leaking. The sec-ond part of the test will determine if engine vacuum(full-manifold) is flowing from the inlet to the outletside of the valve control. This is not to be used as acomplete test of the EGR system.

(1) Electrical operation of the valve control shouldfirst be checked with the DRB scan tool before pro-ceeding with the vacuum test. Refer to the appropri-ate Powertrain Diagnostic Procedures service manualfor operation of the DRB scan tool.

(2) Disconnect the rubber back-pressure hose fromthe fitting at the bottom of EGR valve control (Fig.2).

(3) Connect a hand-held vacuum pump to this fit-ting.

(4) Apply 10 inches of vacuum to this fitting.(5) If vacuum falls off, the valve control diaphragm

is leaking.(6) Replace the EGR valve control. Proceed to next

step for further testing.

(7) Remove the rubber hose at the vacuum inletfitting (Fig. 2) on the EGR valve control.

(8) Connect a vacuum gauge to this disconnectedhose.

(9) Start the engine and bring to operating temper-ature. Hold engine speed at approximately 1500 rpm.

(10) Check for steady engine vacuum (full-mani-fold) at this hose.

(11) If engine vacuum (full-manifold) is notpresent, check vacuum line to engine and repair asnecessary before proceeding to next step.

(12) Reconnect the rubber hose to the vacuum in-let fitting (Fig. 2) on the EGR valve control.

(13) Disconnect the rubber hose at the vacuumoutlet fitting (Fig. 2) on the EGR valve control.

(14) Connect a vacuum gauge to this fitting.(15) Disconnect the electrical connector (Fig. 1) at

the valve control. This will simulate an open circuit(no ground from the PCM) at the valve control.

(16) Start the engine and bring to operating tem-perature.

Hold the engine speed to approximately 2000 rpmwhile checking for engine vacuum (full-manifold) atthis fitting. To allow full manifold vacuum toflow through the valve control, exhaust back-pressure must be present at valve control. Itmust be high enough to hold the bleed valve inthe transducer portion of the valve controlclosed. Have a helper momentarily (a second or two)hold a rag over the tailpipe opening to build some ex-haust back-pressure while observing the vacuumgauge. Heavy gloves should be worn. Do not coverthe tailpipe opening for an extended period oftime as damage to components or overheatingmay result.

As temporary back-pressure is built, full manifoldvacuum should be observed at the vacuum controloutlet fitting. Without back-pressure, and engine atapproximately 2000 rpm, the gauge reading will below. This low reading is normal. At idle speed, thegauge reading will be erratic. This is also normal.

(17) If full manifold vacuum is not present at theoutlet fitting, but was present at the inlet fitting, re-place the valve control. Note: The EGR valve, valvecontrol and attaching hoses are serviced as one unit.Refer to EGR Valve Removal/Installation in thisgroup.

OXYGEN (O2S) SENSORFor description, operation, diagnosis and removal/

installation procedures of the O2S sensor, refer toGroup 14, Fuel Systems.


COMPONENT REMOVAL/INSTALLATION

INDEX

page page

Air Cleaner Element . . . . . . . . . . . . . . . . . . . . . . . 15Air Cleaner Housing . . . . . . . . . . . . . . . . . . . . . . . 15EGR Tube—5.2L Engine . . . . . . . . . . . . . . . . . . . . 15EGR Valve Control . . . . . . . . . . . . . . . . . . . . . . . . 16EGR Valve—5.2L Engine . . . . . . . . . . . . . . . . . . . 15Engine Coolant Temperature Sensor . . . . . . . . . . . 15EVAP Canister . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

EVAP Canister Purge Solenoid . . . . . . . . . . . . . . . 17EVAP Canister Purge Solenoid—Duty Cycle . . . . . 17Fuel Tank Filler Tube Cap . . . . . . . . . . . . . . . . . . . 18Oxygen (O2S) Sensor . . . . . . . . . . . . . . . . . . . . . . 18Powertrain Control Module (PCM) . . . . . . . . . . . . . 18Pressure Relief/Rollover Valve . . . . . . . . . . . . . . . . 18

AIR CLEANER HOUSINGRefer to either of the Component Removal/Installa-

tion sections of Group 14, Fuel System for proce-dures.

AIR CLEANER ELEMENTRefer to either of the Component Removal/Installa-

tion sections of Group 14, Fuel System for proce-dures.

ENGINE COOLANT TEMPERATURE SENSORFor description, operation, diagnosis and removal/

installation procedures, refer to the 4.0L or 5.2L sec-tions of Group 14, Fuel Systems.

EGR VALVE—5.2L ENGINE

REMOVALThe EGR valve, EGR valve control (solenoid) and

attaching hoses are serviced as one unit on the 5.2Lengine.

(1) Disconnect vacuum hoses to EGR valve andEGR valve control. Note position of hoses for easierinstallation.

(2) Remove EGR mounting bolts (Figs. 1 or 2).(3) Remove EGR valve and gasket. Discard old

gasket. Clean intake manifold mating surface andcheck for cracks.

INSTALLATION(1) Place new EGR gasket on intake manifold.(2) Install EGR valve. Tighten mounting bolts to

23 Nzm (200 in. lbs.) torque.(3) Connect vacuum hoses to EGR valve and EGR

valve control.

EGR TUBE—5.2L ENGINE

REMOVAL(1) Remove the spark plug cable loom and spark

plug cables from valve cover mounting stud at rear ofright valve cover (Fig. 2). Position spark plug cablesto top of valve cover.

(2) Remove the right exhaust manifold heat shieldnuts/bolts and remove heat shield (Fig. 3).

(3) Disconnect 2 hoses at EGR valve. Note positionof hoses at EGR valve before removal.

(4) Disconnect electrical connector and hoses atEGR valve control. Note position of hoses before re-moval.

(5) Remove 2 EGR valve mounting bolts (Fig. 2)and remove EGR valve. Discard old EGR gasket.

(6) Disconnect electrical connector at engine oilpressure sending unit.

(7) To prevent damage to oil pressure sending unit,a special tool, such as number C-4597 must be used(Fig. 4). Remove sending unit from engine.

(8) Loosen EGR tube mounting nut at intake man-ifold (Fig. 2).

(9) Remove 2 EGR tube mounting bolts at exhaustmanifold (Fig. 2) and remove EGR tube. Discard oldgasket at exhaust manifold.

(10) Remove EGR tube from vehicle.

Fig. 1 EGR Valve Location—5.2L Engines


INSTALLATION(1) Clean the EGR tube and exhaust manifold (at

EGR tube mounting point) of any old gasket mate-rial.

(2) Install a new gasket to exhaust manifold end ofEGR tube and install EGR tube to both manifolds.Tighten tube mounting nut at intake manifold.Tighten 2 mounting bolts at exhaust manifold to 23Nzm (204 in. lbs.) torque.

(3) Coat the threads of the oil pressure sendingunit with thread sealant. Do not allow any of thethread sealant to get into the sending unit opening,or the opening at the engine. Install sending unit toengine and tighten to 14 Nzm (130 in. lbs.) torque. In-stall electrical connector to sending unit.

(4) Clean the intake manifold and EGR valve ofany old gasket material.

(5) Install a new EGR valve gasket at intake man-ifold.

(6) Install EGR valve to intake manifold. Tighten 2EGR bolts to 23 Nzm (200 in. lbs.) torque.

(7) Position EGR valve control and install its elec-trical connector. Connect hoses between EGR valveand EGR valve control.

(8) Install spark plug cable loom and spark plugcables to valve cover mounting stud.

(9) Install heat shield at right exhaust manifold.

EGR VALVE CONTROLThe EGR valve, the EGR valve control (solenoid)

and the connecting hoses are serviced as one unit onthe 5.2L engine. Refer to EGR Valve Removal/Instal-lation for procedures.

EVAP CANISTERThe EVAP canister is located in the left front cor-

ner of vehicle below the left front headlamp (Figs. 5or 6).

REMOVAL(1) Remove the grill. Refer to Group 23, Body.(2) Remove the front bumper/fascia assembly. Re-

fer to Group 23, Body.(3) Disconnect vacuum lines at canister.(4) Remove the three canister mounting nuts (Figs.

5 or 6).(5) Lower the canister through bottom of vehicle.

INSTALLATION(1) Position canister to body.

Fig. 2 EGR Valve Mounting Bolts—5.2L Engines

Fig. 3 Exhaust Manifold Heat Shield—5.2L Engine

Fig. 4 Oil Pressure Sending Unit—Removal/Installation—5.2 L Engine


(2) Install canister mounting nuts. Tighten nuts to6 Nzm (55 in. lbs.) torque.

(3) Connect vacuum lines.(4) Install the front bumper/fascia assembly and

grill. Refer to Group 23, Body.

EVAP CANISTER PURGE SOLENOID—DUTY CYCLE

4.0L ENGINE—CALIFORNIA EMISSIONPACKAGE ONLY

The solenoid is located near the front of the wind-shield washer reservoir bottle (Fig. 7).

REMOVAL(1) Disconnect the electrical connector at the sole-

noid (Fig. 7).(2) Disconnect the vacuum lines at the solenoid.(3) Remove the two bracket mounting nuts and re-

move solenoid.

INSTALLATION(1) Position the solenoid to vehicle.(2) Install and tighten the two bracket mounting

nuts.(3) Connect the vacuum lines to the solenoid.(4) Connect the electrical connector to the solenoid.

EVAP CANISTER PURGE SOLENOID

REMOVAL—5.2L ENGINE(1) Remove air duct at throttle body.(2) Disconnect wiring connector at solenoid (Fig. 8).(3) Disconnect vacuum harness at solenoid (Fig. 8).(4) Remove solenoid and its support bracket from

intake manifold.(5) Remove EVAP canister purge solenoid from en-

gine.

INSTALLATION(1) Install EVAP canister purge solenoid and its

mounting bracket to intake manifold.(2) Connect vacuum harness and wiring connector.(3) Install air duct to throttle body.

Fig. 5 Canister Location—Non-California

Fig. 6 Canister Location—California EmissionPackage—4.0L Only

Fig. 7 Purge Solenoid—4.0L Engine—CaliforniaEmission Package


FUEL TANK FILLER TUBE CAPIf replacement of the fuel tank filler tube cap (fuel

tank cap) is necessary, it must be replaced with anidentical cap to be sure of correct system operation.

OXYGEN (O2S) SENSORFor description, operation, diagnosis and removal/

installation procedures of the O2S sensor, refer toGroup 14, Fuel Systems.

POWERTRAIN CONTROL MODULE (PCM)For removal and installation procedures, refer to

Group 14, Fuel Systems.

PRESSURE RELIEF/ROLLOVER VALVEFor removal and installation procedures, refer to

the Fuel Tank section of Group 14, Fuel Systems.

Fig. 8 EVAP Canister Purge Solenoid—5.2L Engine


Automotive

95ZJ_25.PDF