2002 JEEP GRAND CHEROKEE engine light

The PCM uses the IAC motor to control idle speed
(along with timing) and to reach a desired MAP dur-
ing decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of
the wires are for 12 volts and ground to supply elec-
trical current to the motor windings to operate the
stepper motor in one direction. The other 2 wires are
also for 12 volts and ground to supply electrical cur-
rent to operate the stepper motor in the opposite
direction.
To make the IAC go in the opposite direction, the
PCM just reverses polarity on both windings. If only
1 wire is open, the IAC can only be moved 1 step
(increment) in either direction. To keep the IAC
motor in position when no movement is needed, the
PCM will energize both windings at the same time.
This locks the IAC motor in place.
In the IAC motor system, the PCM will count
every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the
memory is cleared, the PCM no longer knows the
position of the pintle. So at the first key ON, the
PCM drives the IAC motor closed, regardless of
where it was before. This zeros the counter. From
this point the PCM will back out the IAC motor and
keep track of its position again.
When engine rpm is above idle speed, the IAC is
used for the following:
²Off-idle dashpot (throttle blade will close quickly
but idle speed will not stop quickly)
²Deceleration air flow control
²A/C compressor load control (also opens the pas-
sage slightly before the compressor is engaged so
that the engine rpm does not dip down when the
compressor engages)
²Power steering load control
The PCM can control polarity of the circuit to con-
trol direction of the stepper motor.
IAC Stepper Motor Program:The PCM is also
equipped with a memory program that records the
number of steps the IAC stepper motor most recently
advanced to during a certain set of parameters. For
example: The PCM was attempting to maintain a
1000 rpm target during a cold start-up cycle. The last
recorded number of steps for that may have been
125. That value would be recorded in the memory
cell so that the next time the PCM recognizes the
identical conditions, the PCM recalls that 125 steps
were required to maintain the target. This program
allows for greater customer satisfaction due to
greater control of engine idle.
Another function of the memory program, which
occurs when the power steering switch (if equipped),
or the A/C request circuit, requires that the IAC step-
per motor control engine rpm, is the recording of the
last targeted steps into the memory cell. The PCMcan anticipate A/C compressor loads. This is accom-
plished by delaying compressor operation for approx-
imately 0.5 seconds until the PCM moves the IAC
stepper motor to the recorded steps that were loaded
into the memory cell. Using this program helps elim-
inate idle-quality changes as loads change. Finally,
the PCM incorporates a9No-Load9engine speed lim-
iter of approximately 1800 - 2000 rpm, when it rec-
ognizes that the TPS is indicating an idle signal and
IAC motor cannot maintain engine idle.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the IAC motor through the PCM.
REMOVAL
REMOVAL - 4.0L
The IAC motor is located on the throttle body.
(1) Remove air duct and air resonator box at throt-
tle body.
(2) Disconnect electrical connector from IAC motor
(Fig. 40).
(3) Remove two mounting bolts (screws) (Fig. 26).
(4) Remove IAC motor from throttle body.
REMOVAL - 4.7L
(1) Remove air duct and air resonator box at throt-
tle body.
(2) Disconnect electrical connector from IAC motor
(Fig. 36).
(3) Remove two mounting bolts (screws) (Fig. 42).
(4) Remove IAC motor from throttle body.
Fig. 26 Mounting Bolts (Screws)ÐIAC
1 - IDLE AIR CONTROL MOTOR
2 - MOUNTING SCREWS
WJFUEL INJECTION 14 - 45
IDLE AIR CONTROL MOTOR (Continued)

INSTALLATION
INSTALLATION - 4.0L
The TPS is mounted to the throttle body.
The throttle shaft end of throttle body slides into a
socket in the TPS (Fig. 43). The TPS must be
installed so that it can be rotated a few degrees. (If
sensor will not rotate, install sensor with throttle
shaft on other side of socket tangs). The TPS will be
under slight tension when rotated.
(1) Install TPS and retaining screws.
(2) Tighten screws to 7 N´m (60 in. lbs.) torque.
(3) Connect TPS electrical connector to TPS.
(4) Manually operate throttle (by hand) to check
for any TPS binding before starting engine.
INSTALLATION - 4.7L
The throttle shaft end of throttle body slides into a
socket in TPS (Fig. 44). The TPS must be installed so
that it can be rotated a few degrees. If sensor will
not rotate, install sensor with throttle shaft on other
side of socket tangs. The TPS will be under slight
tension when rotated.
(1) Install TPS and two retaining bolts.
(2) Tighten bolts to 7 N´m (60 in. lbs.) torque.
(3) Manually operate throttle control lever by hand
to check for any binding of TPS.
(4) Connect TPS electrical connector to TPS.
(5) Install air duct/air box to throttle body.
Fig. 43 Throttle Position Sensor InstallationÐ4.0L
Engine
1 - TANGS
2 - THROTTLE SHAFT
3 - THROTTLE BODY
4 - TPS
Fig. 44 TPS InstallationÐ4.7L
1 - THROTTLE BODY
2 - LOCATING TANGS
3 - THROTTLE POSITION SENSOR
4 - SOCKET
5 - THROTTLE SHAFT
14 - 58 FUEL INJECTIONWJ
THROTTLE POSITION SENSOR (Continued)

DIAGNOSIS AND TESTING - PUMP LEAKAGE
(1) Possible areas of pump leakage (Fig. 3).
STANDARD PROCEDURE
STANDARD PROCEDURE - INITIAL OPERATION
- 4.0L
WARNING: THE FLUID LEVEL SHOULD BE
CHECKED WITH ENGINE OFF TO PREVENT INJURY
FROM MOVING COMPONENTS.
CAUTION: Use MOPAR Power Steering Fluid or
equivalent. Do not use automatic transmission fluid
and do not overfill.
Wipe filler cap clean, then check the fluid level.
The dipstick should indicateCOLDwhen the fluid is
at normal ambient temperature.
(1) Fill the pump fluid reservoir to the proper level
and let the fluid settle for at least two minutes.
(2) Start the engine and let run for a few seconds
then turn engine off.
(3) Add fluid if necessary. Repeat the above proce-
dure until the fluid level remains constant after run-
ning the engine.
(4) Raise the front wheels off the ground.
(5) Slowly turn the steering wheel right and left,
lightly contacting the wheel stops at least 20 times.(6) Check the fluid level add if necessary.
(7) Lower the vehicle, start the engine and turn
the steering wheel slowly from lock to lock.
(8) Stop the engine and check the fluid level and
refill as required.
(9) If the fluid is extremely foamy or milky look-
ing, allow the vehicle to stand a few minutes and
repeat the procedure.
CAUTION: Do not run a vehicle with foamy fluid for
an extended period. This may cause pump damage.
STANDARD PROCEDURE - INITIAL OPERATION
- 4.7L
WARNING: THE FLUID LEVEL SHOULD BE
CHECKED WITH ENGINE OFF TO PREVENT INJURY
FROM MOVING COMPONENTS.
NOTE: Remove as much of the old fluid out of the
system as possible with a suction tool or by remov-
ing a hose, When a component has failed. Then
refill it with fresh fluid until it is clean. This may
have to be done more than once.
CAUTION: Use MOPAR Power Steering Fluid or
equivalent. Do not use automatic transmission fluid
and do not overfill.
Wipe filler cap clean, then check the fluid level.
The dipstick should indicateCOLDwhen the fluid is
at normal ambient temperature.
(1) Fill the pump fluid reservoir to the proper level
and let the fluid settle for at least two minutes.
(2) Start the engine and let run for a few seconds
then turn engine off.
(3) Add fluid if necessary. Repeat the above proce-
dure until the fluid level remains constant after run-
ning the engine.
(4) Raise the front wheels off the ground.
(5) Slowly turn the steering wheel right and left,
lightly contacting the wheel stops at least 20 times.
(6) Check the fluid level add if necessary.
(7) Lower the vehicle, start the engine, and use
the DRB III to activate the hydraulic fan on full fan
operation.
(8)
Turn the steering wheel slowly from lock to lock.
(9) Stop the engine, check the fluid level and refill
as required and repeat the process
CAUTION: Do not run a vehicle with foamy fluid for
an extended period. This may cause pump damage.
(10) If the fluid is extremely foamy or milky look-
ing, allow the vehicle to stand a few minutes and
repeat the procedure.
Fig. 3 4.0L Power Steering Pump
WJPUMP 19 - 33
PUMP (Continued)

(17) Disconnect throttle valve cable from transmis-
sion bracket and throttle valve lever (Fig. 15).
(18) Disconnect transfer case shift cable from the
transfer case shift lever (Fig. 16).
(19) Remove the clip securing the transfer case
shift cable into the cable support bracket.
(20) Disconnect transmission fluid cooler lines at
transmission fittings and clips.
(21) Support rear of engine with safety stand or
jack.(22) Raise transmission slightly with service jack
to relieve load on crossmember and supports.
(23) Remove bolts securing rear support and cush-
ion to transmission and crossmember (Fig. 17).
(24) Remove bolts attaching crossmember to frame
and remove crossmember.
(25) Remove transfer case (Fig. 18) and (Fig. 19).
Fig. 15 Throttle Valve Cable
1 - THROTTLE VALVE CABLE
2 - THROTTLE VALVE LEVER
3 - THROTTLE BODY
Fig. 16 Transfer Case Shift Cable
1 - TRANSFER CASE SHIFT LEVER
2 - TRANSFER CASE SHIFT CABLE
Fig. 17 Rear Transmission Crossmember
1 - CROSSMEMBER
2 - REAR TRANSMISSION MOUNT
Fig. 18 Remove NV247 Transfer Case
1 - NV247 TRANSFER CASE
21 - 28 AUTOMATIC TRANSMISSION - 42REWJ
AUTOMATIC TRANSMISSION - 42RE (Continued)

(32) Install valve body as follows:
(a) Align and carefully insert park rod into pawl.
Rod will make click noise as it enters pawl. Move
rod slightly to check engagement.
(b) Align and seat valve body on case. Be sure
manual lever shaft and overdrive connector are
fully seated in case. Also be sure valve body wiring
is not pinched or kinked.
(c) Install and start all valve body attaching
bolts by hand. Then tighten bolts evenly, in a diag-
onal pattern to 12 N´m (105 in. lbs.) torque. Do not
overtighten valve body bolts. This could result in
distortion and cross leakage after installation.
CAUTION: It is possible for the park rod to displace
into a cavity just above the pawl sprag during
installation. Make sure the rod is actually engaged
in the pawl and has not displaced into the cavity.
(33) Install new filter on valve body. Tighten filter
screws to 4 N´m (35 in. lbs.).
(34) Adjust front and rear bands.
(35) Install seal on park/neutral position switch.
Then install and tighten switch to 34 N´m (25 ft.
lbs.).
(36) Install magnet in oil pan. Magnet goes on
small protrusion at corner of pan.
(37) Position new oil pan gasket on case and
install oil pan. Tighten pan bolts to 17 N´m (13 ft.
lbs.).
(38) Install new valve body manual shaft seal in
case (Fig. 60). Lubricate seal lip and manual shaft
with petroleum jelly. Start seal over shaft and into
case. Seat seal with 15/16 inch, deep well socket.
(39) Install throttle valve and shift selector levers
on valve body manual lever shaft.INSTALLATION
(1) Check torque converter hub and hub drive
notches for sharp edges burrs, scratches, or nicks.
Polish the hub and notches with 320/400 grit paper
and crocus cloth if necessary. The hub must be
smooth to avoid damaging pump seal during installa-
tion.
(2) Lubricate oil pump seal lip with transmission
fluid.
(3) Align converter and oil pump.
(4) Carefully insert converter in oil pump. Then
rotate converter back and forth until fully seated in
pump gears.
(5) Check converter seating with steel scale and
straightedge (Fig. 61). Surface of converter lugs
should be 1/2 in. to rear of straightedge when con-
verter is fully seated.
(6) Temporarily secure converter with C-clamp.
(7) Position transmission on jack and secure it
with chains.
(8) Check condition of converter driveplate.
Replace the plate if cracked, distorted or damaged.
Also be sure transmission dowel pins are seated in
engine block and protrude far enough to hold trans-
mission in alignment.
(9) Apply a light coating of MopartHigh Temp
grease to the torque converter hub pocket in the rear
of the crankshaft
(10) Raise transmission and align converter with
drive plate and converter housing with engine block.
Fig. 60 Installing Manual Lever Shaft Seal
1 - 15/1688SOCKET
2 - SEAL
Fig. 61 Checking Torque Converter Seating - Typical
1 - SCALE
2 - STRAIGHTEDGE
WJAUTOMATIC TRANSMISSION - 42RE 21 - 41
AUTOMATIC TRANSMISSION - 42RE (Continued)

OVERDRIVE CLUTCH
DESCRIPTION
The overdrive clutch (Fig. 125) is composed of the
pressure plate, clutch plates, holding discs, overdrive
piston retainer, piston, piston spacer, and snap-rings.
The overdrive clutch is the forwardmost component
in the transmission overdrive unit and is considered
a holding component. The overdrive piston retainer,
piston, and piston spacer are located on the rear of
the main transmission case.
NOTE: The number of discs and plates may vary
with each engine and vehicle combination.
OPERATION
To apply the clutch, pressure is applied between
the piston retainer and piston. The fluid pressure is
provided by the oil pump, transferred through the
control valves and passageways, and enters the
clutch through passages at the lower rear portion of
the valve body area. With pressure applied between
the piston retainer and piston, the piston moves
away from the piston retainer and compresses the
clutch pack. This action applies the clutch pack,
allowing torque to flow through the intermediate
shaft into the overdrive planetary gear set. The over-
drive clutch discs are attached to the overdrive clutch
hub while the overdrive clutch plates, reaction plate,
and pressure plate are lugged to the overdrive hous-
ing. This allows the intermediate shaft to transferthe engine torque to the planetary gear and overrun-
ning clutch. This drives the planetary gear inside the
annulus, which is attached to the overdrive clutch
drum and output shaft, creating the desired gear
ratio. The waved snap-ring is used to cushion the
application of the clutch pack.
OVERDRIVE OFF SWITCH
DESCRIPTION
The overdrive OFF (control) switch is located in
the shifter handle. The switch is a momentary con-
tact device that signals the PCM to toggle current
status of the overdrive function.
OPERATION
At key-on, fourth gear operation is allowed. Press-
ing the switch once causes the overdrive OFF mode
to be entered and the overdrive OFF switch lamp to
be illuminated. Pressing the switch a second time
causes normal overdrive operation to be restored and
the overdrive lamp to be turned off. The overdrive
OFF mode defaults to ON after the ignition switch is
cycled OFF and ON. The normal position for the con-
trol switch is the ON position. The switch must be in
this position to energize the solenoid and allow
upshifts to fourth gear. The control switch indicator
light illuminates only when the overdrive switch is
turned to the OFF position, or when illuminated by
the powertrain control module.
Fig. 125 Overdrive Clutch
1 - REACTION PLATE 2 - PRESSURE PLATE
21 - 86 AUTOMATIC TRANSMISSION - 42REWJ

NOTE: Be sure that as the cable is pulled forward
and centered on the throttle lever stud, the cable
housing moves smoothly with the cable. Due to the
angle at which the cable housing enters the spring
housing, the cable housing may bind slightly and
create an incorrect adjustment.
(8) Reconnect the T.V. cable (B) to the throttle
bellcrank lever (C).
(9) Check cable adjustment. Verify transmission
throttle lever and lever on throttle body move simul-
taneously.
TORQUE CONVERTER
DESCRIPTION
The torque converter (Fig. 245) is a hydraulic
device that couples the engine crankshaft to the
transmission. The torque converter consists of an
outer shell with an internal turbine, a stator, an
overrunning clutch, an impeller and an electronically
applied converter clutch. The converter clutch pro-
vides reduced engine speed and greater fuel economy
when engaged. Clutch engagement also provides
reduced transmission fluid temperatures. The torque
converter hub drives the transmission oil (fluid)
pump.
The torque converter is a sealed, welded unit that
is not repairable and is serviced as an assembly.
CAUTION: The torque converter must be replaced if
a transmission failure resulted in large amounts of
metal or fiber contamination in the fluid. If the fluid
is contaminated, flush the all transmission fluid
cooler(s) and lines.
Fig. 244 Throttle Valve Cable at Throttle Linkage
1 - THROTTLE LINKAGE
2 - THROTTLE VALVE CABLE LOCKING CLIP
3 - THROTTLE VALVE CABLE
Fig. 245 Torque Converter Assembly
1 - TURBINE
2 - IMPELLER
3 - HUB
4-STATOR
5 - FRONT COVER
6 - CONVERTER CLUTCH DISC
7 - DRIVE PLATE
21 - 128 AUTOMATIC TRANSMISSION - 42REWJ
THROTTLE VALVE CABLE (Continued)

OPERATION
The converter impeller (Fig. 251) (driving member),
which is integral to the converter housing and bolted
to the engine drive plate, rotates at engine speed.
The converter turbine (driven member), which reacts
from fluid pressure generated by the impeller, rotates
and turns the transmission input shaft.
TURBINE
As the fluid that was put into motion by the impel-
ler blades strikes the blades of the turbine, some of
the energy and rotational force is transferred into the
turbine and the input shaft. This causes both of them
(turbine and input shaft) to rotate in a clockwise
direction following the impeller. As the fluid is leav-
ing the trailing edges of the turbine's blades it con-
tinues in a ªhinderingº direction back toward the
impeller. If the fluid is not redirected before it strikes
the impeller, it will strike the impeller in such a
direction that it would tend to slow it down.
STATOR
Torque multiplication is achieved by locking the
stator's over-running clutch to its shaft (Fig. 252).
Under stall conditions (the turbine is stationary), the
oil leaving the turbine blades strikes the face of the
stator blades and tries to rotate them in a counter-
clockwise direction. When this happens the overrun-
ning clutch of the stator locks and holds the stator
from rotating. With the stator locked, the oil strikes
the stator blades and is redirected into a ªhelpingº
direction before it enters the impeller. This circula-
tion of oil from impeller to turbine, turbine to stator,
and stator to impeller, can produce a maximum
torque multiplication of about 2.4:1. As the turbine
begins to match the speed of the impeller, the fluid
that was hitting the stator in such as way as to
cause it to lock-up is no longer doing so. In this con-
dition of operation, the stator begins to free wheel
and the converter acts as a fluid coupling.
Fig. 251 Torque Converter Fluid Operation
1 - APPLY PRESSURE 3 - RELEASE PRESSURE
2 - THE PISTON MOVES SLIGHTLY FORWARD 4 - THE PISTON MOVES SLIGHTLY REARWARD
21 - 132 AUTOMATIC TRANSMISSION - 42REWJ
TORQUE CONVERTER (Continued)