Gear JEEP GRAND CHEROKEE 2002 WJ / 2.G Workshop Manual

(8) Install anewcollapsible preload spacer on pin-
ion shaft and install pinion gear in the housing (Fig.
84).
(9) Install yoke with Installer C-3718 and Spanner
Wrench 6958 (Fig. 85).(10) Install the yoke washer and a new nut on the
pinion gear and tighten the pinion nut until there is
zero bearing end-play.
(11) Tighten the nut to 298 N´m (220 ft. lbs.).
CAUTION: Never loosen pinion gear nut to decrease
pinion rotating torque and never exceed specified
preload torque. If preload torque or rotating torque
is exceeded a new collapsible spacer must be
installed.
(12) Using Spanner Wrench 6958 and a torque
wrench set at 380 N´m (280 ft. lbs.), (Fig. 86) slowly
tighten the nut in 6.8 N´m (5 ft. lbs.) increments
until the rotating torque is achieved. Measure the
rotating torque frequently to avoid over crushing the
collapsible spacer (Fig. 87).
NOTE: If more than 380 N´m (280 ft. lbs.) torque is
required to crush the collapsible spacer, the spacer
is defective and must be replaced.
Fig. 84 COLLAPSIBLE SPACER
1 - COLLAPSIBLE SPACER
2 - SHOULDER
3 - PINION GEAR
4 - DEPTH SHIM
5 - REAR BEARING
Fig. 85 PINION YOKE INSTALLER
1 - INSTALLER
2 - PINION YOKE
3 - DIFFERENTIAL HOUSING
4 - SPANNER WRENCH
Fig. 86 PINION NUT
1 - SPANNER WRENCH
2 - PIPE
3 - TORQUE WRENCH
3 - 128 REAR AXLE - 226RBAWJ
PINION GEAR/RING GEAR (Continued)

(13) Check bearing rotating torque with a inch
pound torque wrench (Fig. 87). The pinion gear rotat-
ing torque should be:
²
Original Bearings: 1 to 2.25 N´m (10 to 20 in. lbs.).
²New Bearings: 2.8 to 4 N´m (25 to 35 in. lbs.).
(14) Invert the differential case and start two ring
gear bolts. This will provide case-to-ring gear bolt
hole alignment.
(15) Invert the differential case in the vise.
(16) Installnewring gear bolts and alternately
tighten to 129-142 N´m (95-105 ft. lbs.) (Fig. 88).
CAUTION: Never reuse the ring gear bolts. The
bolts can fracture causing extensive damage.
NOTE: If equipped with Veri-LokTdifferential install
oil feed plenum and side bearing.
(17) Install differential in housing.
CAUTION: When installing a Vari-lokTdifferential
(Fig. 89), the oil feed tube must point to the bottom
of the housing. If differential is installed with the oil
feed tube pointed toward the top, the anti-rotation
tabs will be damaged.
(18)
Verify differential bearing preload, gear mesh
and contact pattern. Refer to Ajustments for procedure.
(19) Install differential cover and fill with gear
lubricant.(20) Install the propeller shaft with the reference
marks aligned.
(21) Remove supports and lower vehicle.
Fig. 87 PINION ROTATING TORQUE
1 - PINION YOKE/COMPANION FLANGE
2 - INCH POUND TORQUE WRENCH
Fig. 88 RING GEAR
1 - TORQUE WRENCH
2 - RING GEAR BOLT
3 - RING GEAR
4 - CASE
Fig. 89 VARI-LOK
1 - ANTI-ROTATION TAB
2 - OIL FEED TUBE
WJREAR AXLE - 226RBA 3 - 129
PINION GEAR/RING GEAR (Continued)

ELECTRIC BRAKE
DESCRIPTION
The electronic brake distribution (EBD) functions
like a rear proportioning valve. The EBD system uses
the ABS system to control the slip of the rear wheels
in partial braking range. The braking force of the
rear wheels is controlled electronically by using the
inlet and outlet valves located in the HCU.
OPERATION
Upon entry into EBD the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure the outlet valve for
the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
HCU resulting in a drop in fluid pressure to the rear
brakes. In order to increase the rear brake pressure
the outlet valve is switched off and the inlet valve is
pulsed. This increases the pressure to the rear
brakes. This will continue until the required slip dif-
ference is obtained. At the end of EBD braking (no
brake application) the fluid in the LPA drains back to
the master cylinder by switching on the outlet valve
and draining through the inlet valve check valve. At
the same time the inlet valve is switched on to pre-
vent a hydraulic short circiut in case of another
brake application.
The EBD will remain functional during many ABS
fault modes. If the red and amber warning lamps are
illuminated the EBD may have a fault.
FRONT WHEEL SPEED
SENSOR
DESCRIPTION
A wheel speed sensor is used at each wheel. The
front sensors are mounted to the steering knuckles.
The rear sensors are mounted at the outboard end of
the axle. Tone wheels are mounted to the outboard
ends of the front and rear axle shafts. The gear type
tone wheel serves as the trigger mechanism for each
sensor.
OPERATION
The sensors convert wheel speed into a small digi-
tal signal. The CAB sends 12 volts to the sensors.
The sensor has an internal magneto resistance
bridge that alters the voltage and amperage of the
signal circuit. This voltage and amperage is changed
by magnetic induction when the toothed tone wheel
passes the wheel speed sensor. This digital signal issent to the CAB. The CAB measures the voltage and
amperage of the digital signal for each wheel.
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the front wheel sensor mounting bolt
(Fig. 1).
(3) Remove the sensor from the steering knuckle.
(4) Disengage the sensor wire from the brackets
(Fig. 1)on the steering knuckle.
(5) Disconnect the sensor from the sensor harness
(Fig. 2)and (Fig. 3).
(6) Remove the sensor and wire.
INSTALLATION
(1) Install the sensor on the steering knuckle.
(2) Apply Mopar Lock N' Seal or Loctitet242 to
the sensor mounting bolt. Use new sensor bolt if orig-
inal bolt is worn or damaged.
(3) Install the sensor mounting bolt and tighten
bolt to 12-14 N´m (106-124 in. lbs.).
(4) Engage the grommets on the sensor wire to the
steering knuckle brackets.
(5) Connect the sensor wire to the harness connec-
tor.
(6) Check the sensor wire routing. Be sure the
wire is clear of all chassis components and is not
twisted or kinked at any spot.
(7) Remove the support and lower vehicle.
Fig. 1 Sensor Location
1 - BRACKET
2 - BRACKET
3 - WHEEL SPEED SENSOR
4 - MOUNTING BOLT
WJBRAKES - ABS 5 - 43

(3) Connect the harness to the switch. Be sure the
harness connector is firmly seated.
(4) Place the carpet in position and fold the rear
seat back down.
REAR WHEEL SPEED SENSOR
DESCRIPTION
A wheel speed sensor is used at each wheel. The
front sensors are mounted to the steering knuckles.The rear sensors are mounted at the outboard end of
the axle. Tone wheels are mounted to the outboard
ends of the front and rear axle shafts. The gear type
tone wheel serves as the trigger mechanism for each
sensor.
OPERATION
The sensors convert wheel speed into a small digi-
tal signal. The CAB sends 12 volts to the sensors.
The sensor has an internal magneto resistance
bridge that alters the voltage and amperage of the
signal circuit. This voltage and amperage is changed
by magnetic induction when the toothed tone wheel
passes the wheel speed sensor. This digital signal is
sent to the CAB. The CAB measures the voltage and
amperage of the digital signal for each wheel.
REMOVAL
(1) Raise and fold the rear seat forward. Then
move the carpeting aside for access to the rear sensor
connectors.
(2) Disconnect the rear sensor wire at the harness
connectors (Fig. 7).
(3) Push the sensor wires and grommets through
the floorpan holes.
(4) Raise and support the vehicle.
(5) Disengage the sensor wire from the axle and
the chassis brackets and from the brake line retain-
ers.
(6) Remove the sensor mounting bolt from the rear
brake backing plate. (Fig. 8).
(7) Remove the sensor from the backing plate.
Fig. 5 G-Switch Mounting
1 - MOUNTING BOLTS
2 - CONNECTOR
3 - G-SWITCH
Fig. 6 G-Switch
1 - SWITCH PART NUMBER
2 - ARROW INDICATES FRONT OF SWITCH FOR PROPER
MOUNTING
Fig. 7 Rear Sensor Connector
1 - RIGHT REAR WHEEL SPEED SENSOR CONNECTOR
2 - LEFT REAR WHEEL SPEED SENSOR CONNECTOR
3 - G-SWITCH SENSOR
4 - PARKING BRAKE CABLES
WJBRAKES - ABS 5 - 45
G-SWITCH (Continued)

DESCRIPTION N´m Ft. In.
Lbs. Lbs.
4.0L 4 Ð 32
4.7L 2 Ð 17
Fan Blade Assy. to Viscous
DriveÐ
Bolts 4.0L 23 Ð 200
Generator MountingÐBolts
4.0L57 42 Ð
Radiator Upper Isolator to
CrossmemberÐNuts 3 Ð 20
Radiator Upper Isolator to
RadiatorÐ
Nuts 4 Ð 36
Radiator BraceÐBolts 10 Ð 90
Thermostat HousingÐBolts
4.0L 22 16 Ð
4.7L 13 Ð 115
Upper Radiator Crossmember
to
BodyÐBolts 10 Ð 90
Water PumpÐBolts
4.0L 23 17 Ð
4.7L 54 40 Ð
Water Pump Pulley to Water
PumpÐ
Bolts 4.0L 28 Ð 250
High Pressure Inlet Hose to
Hydraulic Fan DriveÐ1/2 inch
Fitting49 36 Ð
High Pressure Outlet Hose to
Steering GearÐ3/8 inch
Fitting29 21.5 Ð
Fan Shroud to Radiator
Mounting Bolts6Ð50SPECIAL TOOLS
COOLING
Pliers 6094
Pressure Tester 7700±A
WJCOOLING 7 - 15
COOLING (Continued)

²Fan control valve
²Two stage G-rotor hydraulic drive
The hydraulic fan and drive is not serviceable.
Therefore any failure of the fan blade, hydraulic fan
drive or fan shroud requires replacement of the fan
module because the fan blade and hydraulic fan drive
are matched and balanced as a system and servicing
either separately would disrupt this balance.
For hydraulic fluid routing information refer to
(Fig. 5).
CAUTION: Do not attempt to service the hydraulic
cooling fan or fan drive separately replace the cooling
module as an assembly. Failure to do so may cause
severe damage to the hydraulic cooling fan assembly.
OPERATION
The hydraulic radiator cooling fan used on the
Grand Cherokee with the 4.7L engine replaces both
the electric fan and the engine driven mechanical
fan. The use of this hydraulic fan provides the 4.7L
equipped Grand Cherokee with heavy trailer tow
capability while at the same time reducing unneces-
sary power drain on both the engine and the vehicles
electrical system.
HYDRAULIC FAN STRATEGY
The hydraulic radiator cooling fan is controlled by
the JTEC. A PWM (Pulse With Modulated) signal
from the JTEC controls the fan from 0 to 100% of the
available fan speed. There are four inputs to the
JTEC that determine what speed percentage of fan is
required by the vehicle. These inputs are:
²Engine Coolant Temperature
²Transmission Oil Temperature
²Battery Temperature
²A/C System Pressure
By monitoring these four parameters, the JTEC
can determine if cooling airflow is required. If airflow
is required, the JTEC will slowly ramp up (speed up)
the fan speed until the parameter(s) are under con-
trol. Once the temperature or pressure is reduced to
within operating parameters the fan will ramp up,
ramp down, or hold its speed to maintain the temper-
ature / pressure requirements.
NOTE: Even if the JTEC is not requesting fan on
operation the fan blade will usually spin between
100 and 500 RPM when the vehicle is at idle. This is
due to a controlled minimum oil flow requirement
through the fan drive motor.
ACTIVATING THE HYDRAULIC FAN WITH THE DRB
Under the Engine Systems test heading, there is a
subheading. ªHydraulic fan solenoid testº, that has
the selections, on /off. Activating the fan with the
DRB will run the fan at 100% duty cycle, which will
help troubleshoot any system problems, and also help
with the deaeration procedure.
NOTE: Engine must be running to activate the fan
with the DRB.
RADIATOR COOLING FAN HYDRAULIC FLUID PATH
Hydraulic fluid is pumped through the power
steering pump, from the pump the fluid travels
though a high pressure delivery line to the fan drive
motor. As fluid is diverted through the G-rotors, rota-
tional motion is created as fluid moves from the high-
pressure (inlet) side of the motor to the low-pressure
(outlet) side. Fluid exiting the drive motor is divided
into two paths. Path one continues through a high
pressure delivery line to the vehicles steering gear to
provide steering assist. and path two sends fluid
back to the power steering pump through a low pres-
sure line. Fluid exits the steering gear under low
pressure and travels through a low pressure line to
the power steering fluid cooler to be cooled before
being returned back the the power steering fluid res-
ervoir (Fig. 5).
Fig. 4 HYDRAULIC RADIATOR COOLING FAN AND
FAN DRIVE
1 - POWER STEERING FLUID COOLER
2 - RADIATOR
3 - HIGH PRESSURE LINE FROM STEERING GEAR PUMP TO
HYDRAULIC FAN MOTOR
4 - HYDRAULIC FAN MOTOR
5 - HIGH PRESSURE LINE FROM HYDRAULIC FAN MOTOR TO
STEERING GEAR
6 - FAN SHROUD
7 - 28 ENGINEWJ
RADIATOR FAN - 4.7L (Continued)

NOTE: There is a steering flow control valve located
in the fan drive motor. This valve operates like the
flow control valve found in the typical power steer-
ing pump. Because of the design of the valve steer-
ing assist can not be effected by the radiator
cooling fan even during fan drive failure.
REMOVAL
(1) Raise vehicle on hoist.
(2) Drain cooling system.(Refer to 7 - COOLING -
STANDARD PROCEDURE)
NOTE: The hydraulic fan drive is driven by the
power steering pump. When removing lines or
hoses from fan drive assembly use a drain pan to
catch any power steering fluid that may exit the fan
drive or the lines and hoses.NOTE: When ever the high pressure line fittings are
removed from the hydraulic fan drive the O-rings
must be replaced.
(3) Disconnect two high pressure lines at hydraulic
fan drive (Fig. 6). Remove and discard o-rings from
line fittings.
(4) Disconnect low pressure return hose at hydrau-
lic fan drive (Fig. 6).
NOTE: The lower mounting bolts can only be
accessed from under vehicle.
(5) Remove two lower mounting bolts from the
shroud (Fig. 8).
(6) Lower vehicle.
(7) Disconnect the electrical connector for the fan
control solenoid.
(8) Disconnect the radiator upper hose at the radi-
ator and position out of the way.
(9) Disconnect the power steering gear outlet hose
and fluid return hose at the cooler (Fig. 7).
Fig. 5 HYDRAULIC FAN FLUID FLOW CIRCUIT
1 - POWER STEERING RESERVOIR
2 - POWER STEERING PUMP
3 - HYDRAULIC FAN DRIVE ASSEMBLY
4 - FAN BLADE5 - HYDRAULIC FAN CONTROL SOLENOID
6 - POWER STEERING OIL COOLER
7 - STEERING GEAR
WJENGINE 7 - 29
RADIATOR FAN - 4.7L (Continued)

(10) Remove two upper mounting bolts from the
shroud (Fig. 8).
(11) Remove the shroud and fan drive from vehi-
cle.
CLEANING
Clean the fan blades using a mild soap and water.
Do not use an abrasive to clean the blades.
INSTALLATION
CAUTION: There is an external ground wire con-
nected to the hydraulic fan drive located at the elec-
trical connector on the fan assembly. This ground
MUST remain connected at all times. Failure to
ensure ground wire is connected when engine is
operating can cause severe damage to the JTEC
module.
(1) Position fan drive and shroud in vehicle.
(2) Install fan shroud upper mounting bolts. Do
not tighten at this time.
(3) Install radiator upper hose onto radiator.
(4) Connect power steering cooler hoses.
(5) Raise vehicle on hoist.
(6) Install fan shroud lower mounting bolts.
Tighten to 6 N´m (50 in. lbs.).
Fig. 6 HYDRAULIC LINES/HOSES AND ELECTRICAL
CONNECTOR
1 - LOW PRESSURE RETURN HOSE
2 - HIGH PRESSURE LINE (OUTLET)
3 - HIGH PRESSURE LINE (INLET)
4 - HYDRAULIC FAN DRIVE
Fig. 7 POWER STEERING GEAR OUTLET AND
RETURN HOSES
1 - POWER STEERING COOLER RETURN HOSE
2 - POWER STEERING COOLER SUPPLY HOSE
Fig. 8 FAN SHROUD MOUNTING BOLT LOCATIONS
1 - FAN SHROUD UPPER MOUNTING BOLT LOCATIONS
2 - FAN SHROUD LOWER MOUNTING BOLT LOCATIONS
7 - 30 ENGINEWJ
RADIATOR FAN - 4.7L (Continued)

Programmable Communications Interface (PCI) data
bus network.
For diagnosis of the HSM, MHSM or the PCI data
bus, a DRBIIItscan tool and the proper Diagnostic
Procedures manual are recommended. The HSM or
MHSM cannot be repaired and, if faulty or damaged,
it must be replaced.
OPERATION
The MSM receives hard wired inputs from the
power seat switch and the potentiometers on each of
the driver side power seat motors. The MSM receives
messages over the PCI data bus from the Driver
Door Module (DDM) (memory switch status), the
Powertrain Control Module (PCM) (vehicle speed sta-
tus), and the Body Control Module (seat belt switch
status).The MSM will prevent the seat memory recall
function from being initiated if the driver side seat
belt is buckled, if the transmission gear selector lever
is not in the Park or Neutral positions, or if the vehi-
cle is moving.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - HEATED SEAT
MODULE
Visually inspect the related wiring harness connec-
tors. Look for broken, bent, pushed out, or corroded
terminals. If any of the above conditions are present,
repair as necessary. If not, use a DRBIIItscan tool
and the proper Diagnostic Procedures Manual to test
the HSM or MHSM. For complete circuit diagrams,
refer toPower Seat Premium I/IIIin Wiring Dia-
grams.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the driver side front bucket seat from
the power seat track unit. Refer toBucket Seat
Track Adjusterin Body for the procedure.
(3) Lift the heated seat module off of the power
seat track and disconnect the power seat wire har-
ness connectors (Fig. 10).
(4) Remove the module from the bracket.
Fig. 9 Heated Seat Module Remove/Install
1 - NUT (4)
2 - SEAT CUSHION FRAME
3 - POWER SEAT TRACK
4 - STUD (4)
5 - MODULE
6 - BRACKET
Fig. 10 Heated Seat Module Remove/Install
1 - NUT (4)
2 - SEAT CUSHION FRAME
3 - POWER SEAT TRACK
4 - STUD (4)
5 - MODULE
6 - BRACKET
WJELECTRONIC CONTROL MODULES 8E - 11
MEMORY HEATED SEAT/MIRROR MODULE (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)