clutch JEEP GRAND CHEROKEE 2002 WJ / 2.G Owner's Manual

Condition Possible Causes Correction
Gear Teeth Broke 1. Overloading. 1. Replace gears. Examine other
gears and bearings for possible
damage.
2. Erratic clutch operation. 2. Replace gears and examine the
remaining parts for damage. Avoid
erratic clutch operation.
3. Ice-spotted pavement. 3. Replace gears and examine
remaining parts for damage.
4. Improper adjustments. 4. Replace gears and examine
remaining parts for damage. Ensure
ring gear backlash is correct.
Axle Noise 1. Insufficient lubricant. 1. Fill differential with the correct
fluid type and quantity.
2. Improper ring gear and pinion
adjustment.2. Check ring gear and pinion
contact pattern.
3. Unmatched ring gear and pinion. 3. Replace gears with a matched
ring gear and pinion.
4. Worn teeth on ring gear and/or
pinion.4. Replace ring gear and pinion.
5. Loose pinion bearings. 5. Adjust pinion bearing pre-load.
6. Loose differential bearings. 6. Adjust differential bearing
pre-load.
7. Mis-aligned or sprung ring gear. 7. Measure ring gear run-out.
Replace components as necessary.
8. Loose differential bearing cap
bolts.8. Inspect differential components
and replace as necessary. Ensure
that the bearing caps are torqued
tot he proper specification.
9. Housing not machined properly. 9. Replace housing.
VARI-LOKT
(1) Park the vehicle on a level surface or raise
vehicle on hoist so that the vehicle is level.
(2) Remove the axle fill plug.
(3) Verify that the axle fluid level is correct. The
fluid level is correct if the fluid is level with the bot-
tom of the fill hole.
(4) Shift the transfer case into the 4WD full-time
position.
(5) Drive the vehicle in a tight circle for 2 minutes
at 5mph to fully prime the pump.
(6) Block the tires opposite the axle to be tested to
prevent the vehicle from moving.
(7) Shift the transfer case into the 4WD Low posi-
tion and the transmission into the Park position.
(8) Raise both the wheels of the axle to be tested
off of the ground.(9) Rotate the left wheel by hand at a minimum of
one revolution per second while an assistant rotates
the right wheel in the opposite direction.
(10) The left wheel should spin freely at first and
then increase in resistance within 5 revolutions until
the wheels cannot be continuously rotated in opposite
directions.
(11) The Vari-loktdifferential has engaged prop-
erly if the wheels cannot be rotated in opposite direc-
tions for a moment. After the wheels stop rotating for
a moment, the fluid pressure will drop in the differ-
ential and the wheels begin to rotate once again.
(12) If the system does not operate properly,
replace the Vari-loktdifferential.
REMOVAL
(1) Raise and support the vehicle.
(2) Position a lifting device under the axle and
secure axle.
WJREAR AXLE - 226RBA 3 - 95
REAR AXLE - 226RBA (Continued)

(12) Install cover and tighten bolts in a criss-cross
pattern to 41 N´m (30 ft. lbs.).
(13) Refill the differential with Mopar Hypoid
Gear Lubricant or equivalent to bottom of the fill
plug hole.
(14) Install fill hole plug.
(15) Remove support and lower the vehicle.
DIFFERENTIAL - TRAC-LOK
DIAGNOSIS AND TESTING
The most common problem is a chatter noise when
turning corners. Before removing the unit for repair,
drain, flush and refill the axle with the specified
lubricant. A container of Mopar Trac-loktLubricant
(friction modifier) should be added after repair ser-
vice or during a lubricant change.
After changing the lubricant, drive the vehicle and
make 10 to 12 slow, figure-eight turns. This maneu-
ver will pump lubricant through the clutches. This
will correct the condition in most instances. If the
chatter persists, clutch damage could have occurred.
DIFFERENTIAL TEST
The differential can be tested without removing the
differential case by measuring rotating torque. Make
sure brakes are not dragging during this measure-
ment.
(1) Place blocks in front and rear of both front
wheels.
(2) Raise one rear wheel until it is completely off
the ground.
(3) Engine off, transmission in neutral, and park-
ing brake off.
(4) Remove wheel and bolt Special Tool 6790 or
equivalent tool to studs.
(5) Use torque wrench on special tool to rotate
wheel and read rotating torque (Fig. 56).
(6) If rotating torque is less than 41 N´m (56 ft.
lbs.) or more than 271 N´m (200 ft. lbs.) on either
wheel the unit should be serviced.
DISASSEMBLY
(1) Clamp side gear Holding Fixture 6965 in a vise
and position the differential case on the Holding Fix-
ture (Fig. 57).
(2) Remove ring gear if the ring gear is to be
replaced. The Trac-loktdifferential can be serviced
with the ring gear installed.
Fig. 56 ROTATING TORQUE TEST
1 - SPECIAL TOOL WITH BOLT IN CENTER HOLE
2 - TORQUE WRENCH
Fig. 57 DIFFERENTIAL CASE FIXTURE
1 - HOLDING FIXTURE
2 - VISE
3 - DIFFERENTIAL
WJREAR AXLE - 226RBA 3 - 119
DIFFERENTIAL (Continued)

(8) Install Forcing Screw C-6960-4 and tighten
screw to 122 N´m (90 ft. lbs.) maximum to compress
Belleville springs in clutch packs (Fig. 62).
(9) With a feeler gauge remove thrust washers
from behind the pinion gears (Fig. 63).(10) Insert Turning Bar C-6960-2 into the pinion
mate shaft hole in the case (Fig. 64).
(11) Loosen the Forcing Screw in small increments
until the clutch pack tension is relieved and the dif-
ferential case can be turned using Turning Bar.
(12) Rotate differential case until the pinion gears
can be removed.
(13) Remove pinion gears from differential case.
(14) Remove Forcing Screw, Step Plate and
Threaded Adapter.
(15) Remove top side gear, clutch pack retainer
and clutch pack. Keep plates in correct order during
removal (Fig. 65).
(16) Remove differential case from the Holding
Fixture. Remove side gear, clutch pack retainer and
clutch pack. Keep plates in correct order during
removal.
CLEANING
Clean all components in cleaning solvent and dry
components with compressed air.
INSPECTION
Inspect clutch pack plates for wear, scoring or dam-
age. Replace both clutch packs if any one component
in either pack is damaged. Inspect side and pinion
gears for cracks chips or damage and replace as nec-
essary. Inspect differential case and pinion shaft and
replace if worn or damaged.
ASSEMBLY
Clean all components in cleaning solvent and dry
components with compressed air. Inspect clutch pack
plates for wear, scoring or damage. Replace both
clutch packs if any one component in either pack is
Fig. 62 COMPRESS BELLEVILLE SPRING
1 - TORQUE WRENCH
2 - TOOL ASSEMBLED
3 - DIFFERENTIAL CASE
Fig. 63 PINION GEAR THRUST WASHER
1 - THRUST WASHER
2 - FEELER GAUGE
Fig. 64 PINION GEARS
1 - PINION GEARS
2 - TURNING BAR
WJREAR AXLE - 226RBA 3 - 121
DIFFERENTIAL - TRAC-LOK (Continued)

damaged. Inspect side gears and pinions. Replace
any gear that is worn, cracked, chipped or damaged.
Inspect differential case and pinion shaft. Replace if
worn or damaged.
NOTE: New Plates and discs with fiber coating (no
grooves or lines) must be presoaked in Friction
Modifier before assembly. Soak plates and discs for
a minimum of 20 minutes.
(1) Lubricate each component with gear lubricant
before assembly.
(2) Assemble the clutch discs into packs and
secure disc packs with retaining clips (Fig. 66).
NOTE: Dished plate is position with the convex side
against the side gear.
(3) Position assembled clutch disc packs on the
side gear hubs.
(4) Install clutch pack and side gear in the ring
gear side of the differential case (Fig. 67).Be sure
clutch pack retaining clips remain in position
and are seated in the case pockets.
(5) Position the differential case on the Holding
Fixture 6965.
Fig. 65 SIDE GEARS AND CLUTCH DISCS
1 - DIFFERENTIAL CASE
2 - RETAINER
3 - SIDE GEAR AND CLUTCH DISC PACK
Fig. 66 CLUTCH PACK
1 - DISCS
2 - DISHED PLATE
3 - RETAINER
4 - SIDE GEAR
5 - RETAINER
6 - PLATES
Fig. 67 CLUTCH PACK AND LOWER SIDE GEAR
1 - DIFFERENTIAL CASE
2 - LOWER SIDE GEAR AND CLUTCH DISC PACK
3 - 122 REAR AXLE - 226RBAWJ
DIFFERENTIAL - TRAC-LOK (Continued)

(6) Install lubricated Step Plate C-6960-3 in lower
side gear (Fig. 68).
(7) Install the upper side gear and clutch disc pack
(Fig. 68).
(8) Hold assembly in position. Insert Threaded
Adapter C-6960-1 into top side gear.
(9) Install Forcing Screw C-6960-4 and tighten
screw to slightly compress clutch disc.
(10) Place pinion gears in position in side gears
and verify that the pinion mate shaft hole is aligned.
(11) Rotate case with Turning Bar C-6960-2 until
the pinion mate shaft holes in pinion gears align
with holes in case. It may be necessary to slightly
tighten the forcing screw in order to install the pin-
ion gears.
(12) Tighten forcing screw to 122 N´m (90 ft. lbs.)
maximum to compress the Belleville springs.
(13) Lubricate and install thrust washers behind
pinion gears and align washers with a small screw
driver. Insert mate shaft into each pinion gear to ver-
ify alignment.
(14) Remove Forcing Screw, Step Plate and
Threaded Adapter.
(15) Install pinion gear mate shaft and align holes
in shaft and case.(16) Install pinion mate shaft lock screw finger
tight to hold shaft during differential installation.
(17) Lubricate all differential components with
hypoid gear lubricant.
DIFFERENTIAL CASE
BEARINGS
REMOVAL
(1) Remove differential case from axle housing.
(2) Remove side bearings from the differential case
with Puller/Press C-293-PA, Adapters 8353 and Plug
C-293-3 (Fig. 69).
INSTALLATION
NOTE: If differential side bearings or differential
case are replaced, differential side bearing shim
requirements may change. Refer to Adjustments
(Differential Bearing Preload and Gear Backlash) for
procedures.
Fig. 68 CLUTCH PACK AND UPPER SIDE GEAR
1 - SIDE GEAR AND CLUTCH PACK
2 - DIFFERENTIAL CASE
3 - STEP PLATE
Fig. 69 Differential Bearing Removal
1 - ADAPTERS
2 - BEARING
3 - DIFFERENTIAL
4 - PLUG
5 - PULLER
WJREAR AXLE - 226RBA 3 - 123
DIFFERENTIAL - TRAC-LOK (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
17. Viscous fan drive not operating
properly.17. Check fan drive operation and replace as
necessary. (Refer to 7 - COOLING/ENGINE/
FAN DRIVE VISCOUS CLUTCH -
DIAGNOSIS AND TESTING).
18. Cylinder head gasket leaking. 18. Check for cylinder head gasket leaks.
(Refer to 7 - COOLING - DIAGNOSIS AND
TESTING). For repair, (Refer to 9 -
ENGINE/CYLINDER HEAD - REMOVAL).
19. Heater core leaking. 19. Check heater core for leaks. (Refer to 24
- HEATING & AIR CONDITIONING/
PLUMBING/HEATER CORE - REMOVAL).
Repair as necessary.
20. Hydraulic fan speed too low or
inopertive.20. Check for
DTC code.
Check fan operation speeds.
Refer to fan speed operation table.
Low power steering pump output. Refer to
power steering pump diagnosis - 4.7L engine.
TEMPERATURE GAUGE
READING IS
INCONSISTENT
(FLUCTUATES, CYCLES
OR IS ERRATIC)1. During cold weather operation,
with the heater blower in the high
position, the gauge reading may
drop slightly.1. A normal condition. No correction is
necessary.
2. Temperature gauge or engine
mounted gauge sensor defective or
shorted. Also, corroded or loose
wiring in this circuit.2. Check operation of gauge and repair if
necessary. Refer to Group 8J, Instrument
cluster.
3. Gauge reading rises when vehicle
is brought to a stop after heavy use
(engine still running)3. A normal condition. No correction is
necessary. Gauge should return to normal
range after vehicle is driven.
4. Gauge reading high after
re-starting a warmed up (hot)
engine.4. A normal condition. No correction is
necessary. The gauge should return to
normal range after a few minutes of engine
operation.
5. Coolant level low in radiator (air
will build up in the cooling system
causing the thermostat to open late).5. Check and correct coolant leaks. (Refer to
7 - COOLING - DIAGNOSIS AND TESTING).
6. Cylinder head gasket leaking
allowing exhaust gas to enter
cooling system causing a thermostat
to open late.6. (a) Check for cylinder head gasket leaks.
(Refer to 7 - COOLING - DIAGNOSIS AND
TESTING).
(b) Check for coolant in the engine oil.
Inspect for white steam emitting from the
exhaust system. Repair as necessary.
WJCOOLING 7 - 7
COOLING (Continued)

ENGINE
TABLE OF CONTENTS
page page
COOLANT
DESCRIPTION
DESCRIPTION - ENGINE COOLANT.......25
DESCRIPTION - HOAT COOLANT.........25
OPERATION...........................26
COOLANT LEVEL SENSOR
REMOVAL.............................26
INSTALLATION.........................26
COOLANT RECOVERY PRESS CONTAINER
DESCRIPTION.........................27
RADIATOR FAN - 4.7L
DESCRIPTION.........................27
OPERATION...........................28
REMOVAL.............................29
CLEANING............................30
INSTALLATION.........................30
RADIATOR FAN - 4.0L
DESCRIPTION.........................31
REMOVAL.............................31
CLEANING............................32
INSPECTION..........................32
INSTALLATION.........................32
ENGINE BLOCK HEATER
DESCRIPTION
DESCRIPTIONÐ4.7L ENGINE............32
DESCRIPTIONÐ4.0L ENGINE............32
OPERATION...........................33
DIAGNOSIS AND TESTINGÐENGINE BLOCK
HEATER ............................33
REMOVAL
REMOVALÐ4.7L ENGINE...............33
REMOVALÐ4.0L ENGINE...............34
INSTALLATION
INSTALLATIONÐ4.7L ENGINE...........34
INSTALLATIONÐ4.0L ENGINE...........34
ENGINE COOLANT TEMP SENSOR
DESCRIPTION.........................35
OPERATION...........................35
REMOVAL
REMOVALÐ4.0L ENGINE...............35
REMOVALÐ4.7L ENGINE...............36
INSTALLATION
INSTALLATIONÐ4.0L ENGINE...........36
INSTALLATIONÐ4.7L ENGINE...........36
ENGINE COOLANT THERMOSTAT
DESCRIPTION
DESCRIPTIONÐ4.7L ENGINE............36
DESCRIPTIONÐ4.0L ENGINE............37
OPERATION...........................37DIAGNOSIS AND TESTINGÐTHERMOSTAT . . . 37
REMOVAL
REMOVALÐ4.0L ENGINE...............38
REMOVALÐ4.7L ENGINE...............38
INSTALLATION
INSTALLATIONÐ4.0L ENGINE...........38
INSTALLATIONÐ4.7L ENGINE...........39
FAN DRIVE VISCOUS CLUTCH - 4.0L
DESCRIPTION.........................40
OPERATION...........................40
DIAGNOSIS AND TESTINGÐVISCOUS FAN
DRIVE..............................40
PWM FAN CONTROL MODULE - 4.0L
DESCRIPTION.........................41
OPERATION...........................41
REMOVAL.............................41
INSTALLATION.........................42
RADIATOR - 4.7L
DESCRIPTION.........................42
REMOVAL.............................42
CLEANING............................43
INSPECTION..........................44
INSTALLATION.........................44
RADIATOR - 4.0L
DESCRIPTION.........................44
REMOVAL.............................44
CLEANING............................46
INSPECTION..........................47
INSTALLATION.........................47
RADIATOR FAN MOTOR
DIAGNOSIS AND TESTINGÐELECTRIC
COOLING FAN........................47
WATER PUMP - 4.7L
DESCRIPTION
DESCRIPTIONÐWATER PUMP...........47
DESCRIPTIONÐWATER PUMP BYPASS....47
OPERATION
OPERATIONÐWATER PUMP............47
OPERATIONÐWATER PUMP BYPASS.....48
DIAGNOSIS AND TESTINGÐWATER PUMP . . . 48
REMOVAL.............................49
CLEANING............................49
INSPECTION..........................49
INSTALLATION.........................49
WATER PUMP - 4.0L
DESCRIPTION.........................50
DIAGNOSIS AND TESTINGÐWATER PUMP . . . 50
REMOVAL.............................51
CLEANING............................52
7 - 24 ENGINEWJ

FAN DRIVE VISCOUS CLUTCH
- 4.0L
DESCRIPTION
CAUTION: Engines equipped with serpentine drive
belts have reverse rotating fans and viscous fan
drives. They are marked with the word REVERSE to
designate their usage. Installation of the wrong fan
or viscous fan drive can result in engine overheat-
ing.
CAUTION: If the viscous fan drive is replaced
because of mechanical damage, the cooling fan
blades should also be inspected. Inspect for fatigue
cracks, loose blades, or loose rivets that could
have resulted from excessive vibration. Replace fan
blade assembly if any of these conditions are
found. Also inspect water pump bearing and shaft
assembly for any related damage due to a viscous
fan drive malfunction.
The thermal viscous fan drive (Fig. 27) is a sili-
cone-fluid-filled coupling used to connect the fan
blades to the water pump shaft. The coupling allows
the fan to be driven in a normal manner. This is
done at low engine speeds while limiting the top
speed of the fan to a predetermined maximum level
at higher engine speeds.
An electrical cooling fan located in the fan shroud
aids in low speed cooling, It is designed to augment
the viscous fan, However, it does not replace the vis-
cous fan.
OPERATION
A thermostatic bimetallic spring coil is located on
the front face of the viscous fan drive unit (Fig. 27).
This spring coil reacts to the temperature of the radi-
ator discharge air. It engages the viscous fan drive
for higher fan speed if the air temperature from the
radiator rises above a certain point. Until additional
engine cooling is necessary,the fan will remain at
a reduced rpm regardless of engine speed. Nor-
mally less than three hundred (300) rpm.
Only when sufficient heat is present, will the vis-
cous fan drive engage. This is when the air flowing
through the radiator core causes a reaction to the
bimetallic coil. It then increases fan speed to provide
the necessary additional engine cooling.
Once the engine has cooled, the radiator discharge
temperature will drop. The bimetallic coil again
reacts and the fan speed is reduced to the previous
disengaged speed.
DIAGNOSIS AND TESTINGÐVISCOUS FAN
DRIVE
If the fan assembly free-wheels without drag (the
fan blades will revolve more than five turns when
spun by hand), replace the fan drive. This spin test
must be performed when the engine is cool.
For the following test, the cooling system must be
in good condition. It also will ensure against exces-
sively high coolant temperature.
WARNING: BE SURE THAT THERE IS ADEQUATE
FAN BLADE CLEARANCE BEFORE DRILLING.
(1) Drill a 3.18-mm (1/8-in) diameter hole in the
top center of the fan shroud.
(2) Obtain a dial thermometer with an 8 inch stem
(or equivalent). It should have a range of -18É to
105ÉC (0É to 220É F). Insert thermometer through the
hole in the shroud. Be sure that there is adequate
clearance from the fan blades.
(3) Connect a tachometer and an engine ignition
timing light (timing light is to be used as a strobe
light).
(4) Block the air flow through the radiator. Secure
a sheet of plastic in front of the radiator (or air con-
ditioner condenser). Use tape at the top to secure the
plastic and be sure that the air flow is blocked.
(5) Be sure that the air conditioner (if equipped) is
turned off.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR FAN. DO
NOT WEAR LOOSE CLOTHING.
Fig. 27 Viscous Fan Drive
1 - VISCOUS FAN DRIVE
2 - THERMOSTATIC SPRING
3 - MOUNTING NUT TO WATER PUMP HUB
7 - 40 ENGINEWJ

(6) Start the engine and operate at 2400 rpm.
Within ten minutes the air temperature (indicated on
the dial thermometer) should be up to 93É C (200É F).
Fan driveengagementshould have started to occur
at between 91É to 96É C (195É to 205É F). Engage-
ment is distinguishable by a definiteincreasein fan
flow noise (roaring). The timing light also will indi-
cate an increase in the speed of the fan.
(7) When the air temperature reaches 93É C (200É
F), remove the plastic sheet. Fan drivedisengage-
mentshould have started to occur at between 62É to
85É C (145É to 185É F). A definitedecreaseof fan
flow noise (roaring) should be noticed. If not, replace
the defective viscous fan drive unit.
PWM FAN CONTROL MODULE -
4.0L
DESCRIPTION
The pulse width modulated (PWM) radiator cooling
fan relay is located behind the front bumper fascia
below the right headlamp.
OPERATION
The PWM relay is used to control the speed of the
electric radiator cooling fan. It allows for multiple fan
speeds. This allows for improved fan noise and A/C
performance, better engine cooling, and additional
vehicle power.
PWM relay operation is controlled by the Power-
train Control Module (PCM). To operate the PWM
relay, the PCM looks at inputs from:
²Engine coolant temperature
²Ambient temperature from the body controller
²Vehicle speed
²Transmission oil temperature
²A/C switch position (A/C request)
REMOVAL
The Pulse Width Modulated (PWM) cooling fan
relay is located below the right headlamp behind the
bumper fascia (Fig. 28).
(1) Remove front bumper and grill assembly.
(2) Remove 1 support bolt near front of reservoir
(Fig. 28).
(3) Remove 2 reservoir mounting bolts.
(4) Remove reservoir from vehicle to gain access to
vacuum hose (Fig. 29). Disconnect vacuum hose from
reservoir fitting at rear of reservoir.
(5) Disconnect electrical connector at relay (Fig.
30).
(6) Remove 2 relay mounting bolts (Fig. 30) and
remove relay.
Fig. 28 Radiator Cooling Fan Relay Location
1 - RADIATOR FAN RELAY
2 - VACUUM RESERVOIR
3 - BOLT
4 - RIGHT FRONT FENDER
Fig. 29 Vacuum Reservoir Removal/Installation
1 - VACUUM HOSE
2 - RADIATOR
3 - VACUUM RESERVOIR
WJENGINE 7 - 41
FAN DRIVE VISCOUS CLUTCH - 4.0L (Continued)

²The PCM pre-positions the idle air control (IAC)
motor.
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the engine coolant tempera-
ture sensor input. The PCM modifies fuel strategy
based on this input.
²Intake manifold air temperature sensor input is
monitored.
²Throttle position sensor (TPS) is monitored.
²The auto shutdown (ASD) relay is energized by
the PCM for approximately three seconds.
²The fuel pump is energized through the fuel
pump relay by the PCM. The fuel pump will operate
for approximately three seconds unless the engine is
operating or the starter motor is engaged.
²The O2S sensor heater element is energized via
the O2S relays. The O2S sensor input is not used by
the PCM to calibrate air-fuel ratio during this mode
of operation.
ENGINE START-UP MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The PCM receives inputs from:
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Starter motor relay
²Camshaft position sensor signal
The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position
sensor signal within approximately 3 seconds of
cranking the engine, it will shut down the fuel injec-
tion system.
The fuel pump is activated by the PCM through
the fuel pump relay.
Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
The PCM determines the proper ignition timing
according to input received from the crankshaft posi-
tion sensor.
ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warm-
up, the PCM receives inputs from:
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
Based on these inputs the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
²The PCM adjusts engine idle speed through the
idle air control (IAC) motor and adjusts ignition tim-
ing.
²The PCM operates the A/C compressor clutch
through the clutch relay. This is done if A/C has been
selected by the vehicle operator and requested by the
A/C thermostat.
²When engine has reached operating tempera-
ture, the PCM will begin monitoring O2S sensor
input. The system will then leave the warm-up mode
and go into closed loop operation.
IDLE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At idle speed, the PCM
receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Battery voltage
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Oxygen sensors
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
injection sequence and injector pulse width by turn-
ing the ground circuit to each individual injector on
and off.
²The PCM monitors the O2S sensor input and
adjusts air-fuel ratio by varying injector pulse width.
It also adjusts engine idle speed through the idle air
control (IAC) motor.
²The PCM adjusts ignition timing by increasing
and decreasing spark advance.
WJELECTRONIC CONTROL MODULES 8E - 13
POWERTRAIN CONTROL MODULE (Continued)