2002 JEEP GRAND CHEROKEE Power train

TRANSMISSION IDENTIFICATION
Transmission identification numbers are stamped
on the left side of the case just above the oil pan
sealing surface (Fig. 1). Refer to this information
when ordering replacement parts. A label is attached
to the transmission case above the stamped numbers.
The label gives additional information which may
also be necessary for identification purposes.
GEAR RATIOS The 545RFE gear ratios are:
1st .................................3.00:1
2nd.................................1.67:1
2nd Prime............................1.50:1
3rd .................................1.00:1
4th .................................0.75:1
5th .................................0.67:1
Reverse..............................3.00:1
OPERATION
The 545RFE offers full electronic control of all auto-
matic up and downshifts, and features real-time adap-
tive closed-loop shift and pressure control. Electronic
shift and torque converter clutch controls help protect
the transmission from damage due to high tempera-
tures, which can occur under severe operating condi-
tions. By altering shift schedules, line pressure, and
converter clutch control, these controls reduce heat gen-
eration and increase transmission cooling.
To help reduce efficiency-robbing parasitic losses,
the transmission includes a dual-stage transmission
fluid pump with electronic output pressure control.
Under most driving conditions, pump output pres-
sure greatly exceeds that which is needed to keep the
clutches applied. The 545RFE pump-pressure controlsystem monitors input torque and adjusts the pump
pressure accordingly. The primary stage of the pump
works continuously; the second stage is bypassed
when demand is low. The control system also moni-
tors input and output speed and, if incipient clutch
slip is observed, the pressure control solenoid duty
cycle is varied, increasing pressure in proportion to
demand.
A high-travel torque converter damper assembly
allows earlier torque converter clutch engagement to
reduce slippage. Needle-type thrust bearings reduce
internal friction. The 545RFE is packaged in a one-
piece die-cast aluminum case. To reduce NVH, the
case has high lateral, vertical and torsional stiffness.
It is also designed to maximize the benefit of the
structural dust cover that connects the bottom of the
bell housing to the engine bedplate, enhancing over-
all power train stiffness. Dual filters protect the
pump and other components. A pump return filter is
added to the customary main sump filter. Indepen-
dent lubrication and cooler circuits assure ample
pressure for normal transmission operation even if
the cooler is obstructed or the fluid cannot flow due
to extremely low temperatures.
The hydraulic control system design (without elec-
tronic assist) provides the transmission with PARK,
REVERSE, NEUTRAL, SECOND, and THIRD gears,
based solely on driver shift lever selection. This
design allows the vehicle to be driven (in ªlimp-inº
mode) in the event of a electronic control system fail-
ure, or a situation that the Transmission Control
Module (TCM) recognizes as potentially damaging to
the transmission.
The TCM also performs certain self-diagnostic
functions and provides comprehensive information
(sensor data, DTC's, etc.) which is helpful in proper
diagnosis and repair. This information can be viewed
with the DRB scan tool.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AUTOMATIC
TRANSMISSION
CAUTION: Before attempting any repair on a
545RFE automatic transmission, check for Diagnos-
tic Trouble Codes with the DRBTscan tool.
Transmission malfunctions may be caused by these
general conditions:
²Poor engine performance
²Improper adjustments
²Hydraulic malfunctions
²Mechanical malfunctions
²Electronic malfunctions
Fig. 1 Transmission Part And Serial Number
Location
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 179
AUTOMATIC TRANSMISSION - 545RFE (Continued)

STATOR
The stator assembly (Fig. 112) is mounted on a sta-
tionary shaft which is an integral part of the oil
pump. The stator is located between the impeller and
turbine within the torque converter case (Fig. 113).
The stator contains an over-running clutch, which
allows the stator to rotate only in a clockwise direc-
tion. When the stator is locked against the over-run-
ning clutch, the torque multiplication feature of the
torque converter is operational.
TORQUE CONVERTER CLUTCH (TCC)
The TCC (Fig. 114) was installed to improve the
efficiency of the torque converter that is lost to the
slippage of the fluid coupling. Although the fluid cou-
pling provides smooth, shock-free power transfer, it is
natural for all fluid couplings to slip. If the impeller
and turbine were mechanically locked together, a
zero slippage condition could be obtained. A hydraulic
piston with friction material was added to the tur-
bine assembly to provide this mechanical lock-up.
In order to reduce heat build-up in the transmission
and buffer the powertrain against torsional vibrations,
the TCM can duty cycle the L/R-CC Solenoid to achieve
a smooth application of the torque converter clutch.
This function, referred to as Electronically Modulated
Converter Clutch (EMCC) can occur at various times
depending on the following variables:
²Shift lever position
²Current gear range
²Transmission fluid temperature
²Engine coolant temperature
²Input speed
²Throttle angle
²Engine speed
Fig. 112 Stator Components
1 - CAM (OUTER RACE)
2 - ROLLER
3 - SPRING
4 - INNER RACE
Fig. 113 Stator Location
1-STATOR
2 - IMPELLER
3 - FLUID FLOW
4 - TURBINE
Fig. 114 Torque Converter Clutch (TCC)
1 - IMPELLER FRONT COVER
2 - THRUST WASHER ASSEMBLY
3 - IMPELLER
4-STATOR
5 - TURBINE
6 - PISTON
7 - FRICTION DISC
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 267
TORQUE CONVERTER (Continued)

POSITION SENSOR
DESCRIPTION
The transfer case position sensor (Fig. 95) is an
electronic device whose output can be interpreted to
indicate the transfer case's current operating mode.
The sensor consists of a five position, resistive multi-
plexed circuit which returns a specific resistance
value to the Powertrain Control Module (PCM) for
each transfer case operating mode. The sensor is
located on the top of the transfer case, just left of the
transfer case centerline and rides against the sector
plate roostercomb. The PCM supplies 5VDC (+/-
0.5V) to the sensor and monitors the return voltage
to determine the sector plate, and therefore the
transfer case, position.
OPERATION
During normal vehicle operation, the Powertrain
Control Module (PCM) monitors the transfer case
position sensor return voltage to determine the oper-
ating mode of the transfer case. Refer to the Operat-
ing Mode Versus Resistance table for the correct
resistance for each position (Fig. 96).
OPERATING MODE VERSUS RESISTANCE
SENSOR POSITION OPERATING MODE SENSOR RESISTANCE (ohms)
1 2WD 1124-1243
2 4WD PART TIME 650-719
3 4WD FULL TIME 389-431
4 NEUTRAL 199-221
5 4WD LOW 57-64
Fig. 96 Position Sensor Linear Movement
1 - POSITION 1 - 10mm  0.5mm
2 - POSITION 2 - 12mm  0.5mm
3 - POSITION 3 - 14mm  0.5mm
4 - POSITION 4 - 16mm  0.5mm
5 - POSITION 5 - 18mm  0.5mm
6 - POSITION 6 - 20mm 0.5mm - FULL EXTENSION
Fig. 95 Transfer Case Position Sensor and
Connector
1 - TRANSFER CASE POSITION SENSOR CONNECTOR
2 - TRANSFER CASE POSITION SENSOR
3 - TRANSFER CASE
4 - OUTPUT SPEED SENSOR CONNECTOR
WJTRANSFER CASE - NV242 21 - 311

FRONT HEADREST SLEEVE
REMOVAL
(1) Remove head restraint (Refer to 23 - BODY/
SEATS/FRONT HEADREST - REMOVAL).
(2) Remove seat back cover (Refer to 23 - BODY/
SEATS/FRONT SEAT BACK COVER - REMOVAL).
(3) Remove hog rings attaching cushion pad to
seat back frame (Fig. 2).
(4) Remove cushion pad from seat back frame.
(5) Rotate head restraint sleeve 1/4 turn counter-
clockwise to release retaining tab.
(6) Pull sleeve from seat back frame (Fig. 3).
INSTALLATION
(1) Position sleeve in seat back frame.
(2) Rotate head restraint sleeve 1/4 turn clockwise
to engage retaining tab.
(3) Install cushion pad onto seat back frame.
(4) Install hog rings attaching cushion pad to seat
back frame.
(5)
Install seat back cover (Refer to 23 - BODY/
SEATS/FRONT SEAT BACK COVER - INSTALLATION).
(6) Install head restraint (Refer to 23 - BODY/
SEATS/FRONT HEADREST - INSTALLATION).
FRONT SEAT
REMOVAL
(1) Move seat to full rearward position.(2) Remove front bolts attaching seat to floor pan
(Fig. 4).
(3) Move seat to full forward position.
(4) Using a trim stick, pry cover from seat track
(power seat only).
(5) Remove rear bolts attaching seat to floor pan.
(6) If equipped, disconnect power seat wire har-
ness connector.
(7) Remove seat from vehicle.
Fig. 2 Cushion Pad
1 - HOG RING
2 - SEAT BACK CUSHION PAD
Fig. 3 Head Restraint Sleeve
1 - HEAD RESTRAINT SLEEVE
2 - SEAT BACK FRAME
3 - RETAINING TAB
Fig. 4 Front Bucket Seat
1 - POWER BUCKET SEAT
2 - FLOOR PAN
3 - SEAT TRACK COVER
23 - 84 SEATSWJ

INSTALLATION
(1) Position seat on floor pan.
(2) If equipped, connect power seat wire harness
connector.
(3) Install rear bolts attaching seat to floor pan.
Tighten bolts to 40 N´m (30 ft. lbs.) torque.
(4) If equipped, install cover on seat track.
(5) Move seat to full rearward position.
(6) Install front bolts attaching seat to floor pan.
Tighten bolts to 40 N´m (30 ft. lbs.) torque.
FRONT SEAT BACK
REMOVAL
(1) Move seat to full rearward position.
(2) Remove inboard bolt attaching seat back frame
to seat cushion frame.
(3) Move seat to full forward position.
(4) Move seat back to full recline position.
(5) Remove screws attaching seat side shield to
seat frame.
(6) Disconnect wire harness connector from
recliner motor, if equipped.
(7) From the underside of the seat, disconnect the
wire harness connector for the power lumber and/or
heated seat, if equipped.
(8) Remove outboard bolts attaching recliner to
seat cushion frame.
(9) Route the power lumber and/or heated seat
harness through the seat cushion cover, if equipped.
(10) Separate seat back from seat cushion.
INSTALLATION
(1) Position seat back on seat cushion.
(2) Route the power lumber and heater harness
through the seat cushion cover, if equipped.
(3) Install recliner bolts attaching seat back frame
to seat cushion frame. Tighten bolts to 28 N´m (20 ft.
lbs.) torque.
(4) Install the inboard bolt attaching seat back
frame to seat cushion frame. Tighten bolt to 47N´m
(35 ft.lbs.).
(5) Connect wire harness connector to recliner
motor and/or heated seat, if equipped.
(6) From the underside of the seat, connect the
power lumber and/or heated seat wire harness con-
nector to the seat harness, if equipped.
(7) Install screws attaching seat side shield to seat
frame.
FRONT SEAT BACK COVER
REMOVAL
(1) Remove head restraint (Refer to 23 - BODY/
SEATS/FRONT HEADREST - REMOVAL).
(2) Using a trim stick, carefully pry head restraint
release button caps from the top of seat back.
(3) Remove seat back (Refer to 23 - BODY/SEATS/
FRONT SEAT BACK - REMOVAL).
(4) Disengage J-strap at base of seat back.
(5) Slide hand between the face of the seat back
pad and the cushion cover and carefully separate
hook and loop fastener (Fig. 5).
(6) Roll cover upward and disengage hog rings.
(7) Roll cover upward to top of seat back.
(8) Separate cover from seat back.
INSTALLATION
(1) Position cover inside-out at the top of seat
back.
(2) Roll cover downward.
(3) Engage hog rings.
(4) Align seat back cover with hook and loop fas-
teners and secure.
(5) Roll cover downward.
(6) Engage J-strap at base of seat back.
(7) Install seat back (Refer to 23 - BODY/SEATS/
FRONT SEAT BACK - INSTALLATION).
NOTE: The taller head restraint release button cap
is positioned on the left hand side and the head
restraint button cap with the hidden button is posi-
tioned on the right hand side.
Fig. 5 Seat Back Cover
1 - SEAT BACK COVER
2 - HOOK AND LOOP FASTENER
3 - SEAT BACK PAD
WJSEATS 23 - 85
FRONT SEAT (Continued)

(8) Position head restraint release button caps on
head restraint sleeves and press to secure.
(9) Install head restraint (Refer to 23 - BODY/
SEATS/FRONT HEADREST - INSTALLATION).
FRONT SEAT CUSHION/COVER
REMOVAL
(1) Remove seat from vehicle (Refer to 23 - BODY/
SEATS/FRONT SEAT - REMOVAL).
(2) Remove seat back (Refer to 23 - BODY/SEATS/
FRONT SEAT BACK - REMOVAL).
(3) Disengage J-straps attaching cushion cover to
seat cushion frame.
(4) Disengage hog rings attaching cushion cover to
cushion frame at rear of seat along bottom of cushion
cover (Fig. 6).
(5) Roll up edges of cover and route seat function
switches through access hole on outboard side of seat
cushion, if equipped.
(6) Disengage seat cushion heater element connec-
tor, if equipped.
(7) Disengage hog rings attaching cover to cushion
along cover insert.
(8) Separate seat cushion cover from seat cushion.
INSTALLATION
(1) Position seat cover on cushion.
(2) Engage hog rings attaching cushion cover to
cushion along insert.
(3) Engage seat cushion heater element connector,
if equipped.
(4) Route seat function switches through access
hole on outboard side of seat cushion, if equipped.(5) Engage J-straps attaching cushion cover to seat
cushion frame.
(6) Engage hog rings attaching cushion cover to
cushion frame.
(7) Install seat back (Refer to 23 - BODY/SEATS/
FRONT SEAT BACK - INSTALLATION).
(8) Install seat (Refer to 23 - BODY/SEATS/
FRONT SEAT - INSTALLATION).
FRONT SEAT SIDE SHIELD
REMOVAL
(1) Remove screws attaching side shield to seat
frame.
(2) Disconnect wire harness connectors from power
seat and power lumbar switches, if equipped.
(3) Separate side shield from seat.
INSTALLATION
(1) Position side shield on seat.
(2) Connect wire harness connectors to power seat
and power lumbar switches, if equipped.
(3) Install screws attaching side shield to seat
frame.
SEAT TRACK & RECLINER
ASSEMBLY
REMOVAL
(1) Remove seat back (Refer to 23 - BODY/SEATS/
FRONT SEAT BACK - REMOVAL).
(2) Disengage J-strap at base of seat back.
(3) Roll seat back cover upward to access bolts
attaching recliner to seat back frame.
(4) Remove bolts attaching recliner to seat back
frame.
(5) Separate recliner from seat back.
INSTALLATION
(1) Position recliner on seat back.
(2) Install bolts attaching recliner to seat back
frame. Tighten bolts to 28 N´m (20 ft. lbs.) torque.
(3) Roll seat back cover downward.
(4) Engage J-strap at base of seat back.
(5) Install seat back (Refer to 23 - BODY/SEATS/
FRONT SEAT BACK - INSTALLATION).Fig. 6 Seat Cushion Cover
1 - HOG RING
2 - CUSHION COVER
23 - 86 SEATSWJ
FRONT SEAT BACK COVER (Continued)

(9) Compare the compressor discharge pressure to
the Performance Temperature and Pressure chart. If
the compressor discharge pressure is high, see the
Pressure Diagnosis chart.
Pressure Diagnosis
Condition Possible Causes Correction
Rapid compressor clutch
cycling (ten or more cycles
per minute).1. Low refrigerant system
charge.1. See Plumbing/Diagnosis and Testing -
Refrigerant System Leaks in this group. Test the
refrigerant system for leaks. Repair, evacuate and
charge the refrigerant system, if required.
Equal pressures, but the
compressor clutch does not
engage.1. No refrigerant in the
refrigerant system.1. See Plumbing/Diagnosis and Testing -
Refrigerant System Leaks in this group. Test the
refrigerant system for leaks. Repair, evacuate and
charge the refrigerant system, if required.
2. Faulty fuse. 2. Check the fuses in the Power Distribution
Center and the junction block. Repair the shorted
circuit or component and replace the fuses, if
required.
3. Faulty a/c compressor
clutch coil.3. See A/C Compressor/Diagnosis and Testing -
Compressor Clutch Coil in this group. Test the
compressor clutch coil and replace, if required.
4. Faulty compressor clutch
relay.4. See A/C Compressor Clutch Relay/Diagnosis
and Testing - Compressor Clutch Relay in this
group. Test the compressor clutch relay and relay
circuits. Repair the circuits or replace the relay, if
required.
6. Faulty a/c high pressure
transducer.6. See A/C High Pressure Transducer/Diagnosis
and Testing in this group. Test the a/c high
pressure transducer and replace, if required.
7. Faulty Fin Probe. 7. Check for open circuit.
8. Faulty Powertrain Control
Module (PCM).8. Refer to the proper Diagnostic Procedures
manual for testing of the PCM. Test the PCM and
replace, if required.
Normal pressures, but A/C
Performance Test air
temperatures at center panel
outlet are too high.1. Excessive refrigerant oil in
system.1. See Refrigerant Oil/Standard Procedure -
Refrigerant Oil Level in this group. Recover the
refrigerant from the refrigerant system and
inspect the refrigerant oil content. Restore the
refrigerant oil to the proper level, if required.
2. Blend door inoperative or
sealing improperly.2. See Blend Door in this group. Inspect the
blend door for proper operation and sealing and
correct, if required.
3. Blend door actuator faulty
or inoperative.3. Perform blend door actuator diagnosis, replace
if faulty.
24 - 4 HEATING & AIR CONDITIONINGWJ
HEATING & AIR CONDITIONING (Continued)

A/C COMPRESSOR CLUTCH
DESCRIPTION
The compressor clutch assembly consists of a sta-
tionary electromagnetic coil, a hub bearing and pul-
ley assembly, and a clutch plate (Fig. 4). The
electromagnetic coil unit and the hub bearing and
pulley assembly are each retained on the nose of the
compressor front housing with snap rings. The clutch
plate is keyed to the compressor shaft and secured
with a bolt.
OPERATION
The compressor clutch components provide the
means to engage and disengage the compressor from
the engine serpentine accessory drive belt. When the
clutch coil is energized, it magnetically draws the
clutch into contact with the pulley and drives the
compressor shaft. When the coil is not energized, the
pulley freewheels on the clutch hub bearing, which is
part of the pulley. The compressor clutch and coil are
the only serviced parts on the compressor.
The compressor clutch engagement is controlled by
several components: the a/c switch on the a/c heater
control panel, the Automatic Zone Control (AZC) con-
trol module (if the vehicle is so equipped), the evap-
orator probe, the a/c high pressure transducer, the
a/c compressor clutch relay, the body control module
(BCM) and the Powertrain Control Module (PCM).
The PCM may delay compressor clutch engagement
for up to thirty seconds. Refer to Electronic Control
Modules for more information on the PCM controls.
DIAGNOSIS AND TESTING - COMPRESSOR
CLUTCH COIL
For circuit descriptions and diagrams, refer to the
appropriate wiring diagrams. The battery must be
fully-charged before performing the following tests.
Refer to Battery for more information.
(1) Connect an ammeter (0 to 10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0 to 20 volt scale) with clip-type leads for measuring
the voltage across the battery and the compressor
clutch coil.
(2) With the a/c heater mode control switch in any
a/c mode, the a/c heater control a/c switch in the ON
position, and the blower motor switch in the lowest
speed position, start the engine and run it at normal
idle.
(3) The compressor clutch coil voltage should read
within 0.2 volts of the battery voltage. If there is
voltage at the clutch coil, but the reading is not
within 0.2 volts of the battery voltage, test the clutch
coil feed circuit for excessive voltage drop and repair
as required. If there is no voltage reading at the
clutch coil, use a DRBIIItscan tool and the appro-
priate diagnostic information for testing of the com-
pressor clutch circuit. The following components
must be checked and repaired as required before you
can complete testing of the clutch coil:
²Fuses in the junction block and the Power Dis-
tribution Center (PDC)
²A/C heater mode control switch
²A/C compressor clutch relay
²A/C high pressure transducer
²A/C evaporator probe
²Powertrain Control Module (PCM)
²Body Control Module (BCM)
(4) The compressor clutch coil is acceptable if the
current draw measured at the clutch coil is 2.0 to 3.9
amperes with the electrical system voltage at 11.5 to
12.5 volts. This should only be checked with the work
area temperature at 21É C (70É F). If system voltage
is more than 12.5 volts, add electrical loads by turn-
ing on electrical accessories until the system voltage
drops below 12.5 volts.
(a) If the clutch coil current reading is four
amperes or more, the coil is shorted and should be
replaced.
(b) If the clutch coil current reading is zero, the
coil is open and should be replaced.
Fig. 4 COMPRESSOR CLUTCH - TYPICAL
1 - CLUTCH PLATE
2 - SHAFT KEY
3 - PULLEY
4 - COIL
5 - CLUTCH SHIMS
6 - SNAP RING
7 - SNAP RING
WJCONTROLS 24 - 13