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

INSTALLATION
(1) Install the MHSM,HSM into the bracket.
(2) Position the heated seat module and mounting
bracket onto the power seat track.
(3) Reconnect the power seat wiring harness con-
nectors to the heated seat module.
(4) Install the driver side front bucket seat onto
the power seat track unit (Refer to 23 - BODY/
SEATS/SEAT TRACK ADJUSTER - INSTALLA-
TION).
(5) Reconnect the battery negative cable.
NOTE: If the vehicle is equipped with the optional
Memory System, following installation, it will be
necessary to initialize the Memory Heated Seat
Module (MHSM). In order to function properly, the
MHSM must ªlearnº the sensor values of each of
the power seat motor position transducers in each
of the adjuster hard stop positions. This is done by
performing the ªReset Guard Bandº procedure
using a DRBIIITscan tool and the proper Diagnostic
Procedures manual.
WARNING: THE ªRESET GUARD BANDº PROCE-
DURE WILL CAUSE THE DRIVER SIDE FRONT
SEAT TO AUTOMATICALLY ADJUST TO EACH OF
ITS TRAVEL LIMITS. BE CERTAIN THAT NO ONE IS
SEATED IN THE VEHICLE AND THAT THERE IS
NOTHING IN THE VEHICLE THAT WILL OBSTRUCT
SEAT MOVEMENT. FAILURE TO OBSERVE THIS
WARNING COULD RESULT IN PERSONAL INJURIES
AND/OR VEHICLE DAMAGE.
POWERTRAIN CONTROL
MODULE
DESCRIPTION
DESCRIPTION - PCM
The Powertrain Control Module (PCM) is located
in the engine compartment (Fig. 11). The PCM is
referred to as JTEC.
MODES OF OPERATION
As input signals to the Powertrain Control Module
(PCM) change, the PCM adjusts its response to the
output devices. For example, the PCM must calculate
different injector pulse width and ignition timing for
idle than it does for wide open throttle (WOT).
The PCM will operate in two different modes:
Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input
signals and responds only according to preset PCMprogramming. Input from the oxygen (O2S) sensors
is not monitored during Open Loop modes.
During Closed Loop modes, the PCM will monitor
the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector
pulse width results in the ideal air-fuel ratio. This
ratio is 14.7 parts air-to-1 part fuel. By monitoring
the exhaust oxygen content through the O2S sensor,
the PCM can fine tune the injector pulse width. This
is done to achieve optimum fuel economy combined
with low emission engine performance.
The fuel injection system has the following modes
of operation:
²Ignition switch ON
²Engine start-up (crank)
²Engine warm-up
²Idle
²Cruise
²Acceleration
²Deceleration
²Wide open throttle (WOT)
²Ignition switch OFF
The ignition switch On, engine start-up (crank),
engine warm-up, acceleration, deceleration and wide
open throttle modes are Open Loop modes. The idle
and cruise modes, (with the engine at operating tem-
perature) are Closed Loop modes.
IGNITION SWITCH (KEY-ON) MODE
This is an Open Loop mode. When the fuel system
is activated by the ignition switch, the following
actions occur:
Fig. 11 PCM Location
1 - PCM
2 - COOLANT TANK
8E - 12 ELECTRONIC CONTROL MODULESWJ
MEMORY HEATED SEAT/MIRROR MODULE (Continued)

²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
CRUISE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At cruising speed, the PCM
receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake 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)
²Oxygen (O2S) 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 adjust
the injector pulse width by turning the ground circuit
to each individual injector on and off.
²The PCM monitors the O2S sensor input and
adjusts air-fuel ratio. It also adjusts engine idle
speed through the idle air control (IAC) motor.
²The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
ACCELERATION MODE
This is an Open Loop mode. The PCM recognizes
an abrupt increase in throttle position or MAP pres-
sure as a demand for increased engine output and
vehicle acceleration. The PCM increases injector
pulse width in response to increased throttle opening.
DECELERATION MODE
When the engine is at operating temperature, this
is an Open Loop mode. During hard deceleration, the
PCM receives the following inputs.
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Vehicle speed
If the vehicle is under hard deceleration with the
proper rpm and closed throttle conditions, the PCM
will ignore the oxygen sensor input signal. The PCM
will enter a fuel cut-off strategy in which it will not
supply a ground to the injectors. If a hard decelera-
tion does not exist, the PCM will determine the
proper injector pulse width and continue injection.
Based on the above inputs, the PCM will adjust
engine idle speed through the idle air control (IAC)
motor.
The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the PCM receives the following
inputs.
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
During wide open throttle conditions, 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. The PCM ignores the oxygen sensor input
signal and provides a predetermined amount of addi-
tional fuel. This is done by adjusting injector pulse
width.
²The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
IGNITION SWITCH OFF MODE
When ignition switch is turned to OFF position,
the PCM stops operating the injectors, ignition coil,
ASD relay and fuel pump relay.
DESCRIPTION - 5 VOLT SUPPLIES
Two different Powertrain Control Module (PCM)
five volt supply circuits are used; primary and sec-
ondary.
DESCRIPTION - IGNITION CIRCUIT SENSE
This circuit ties the ignition switch to the Power-
train Control Module (PCM).
8E - 14 ELECTRONIC CONTROL MODULESWJ
POWERTRAIN CONTROL MODULE (Continued)

SWITCH
DESCRIPTION
There are two separate switch pods that operate
the speed control system. The steering-wheel-
mounted switches use multiplexed circuits to provide
inputs to the PCM for ON, OFF, RESUME, ACCEL-
ERATE, SET, DECEL and CANCEL modes. Refer to
the owner's manual for more information on speed
control switch functions and setting procedures.
The individual switches cannot be repaired. If one
switch fails, the entire switch module must be
replaced.
OPERATION
When speed control is selected by depressing the
ON, OFF switch, the PCM allows a set speed to be
stored in its RAM for speed control. To store a set
speed, depress the SET switch while the vehicle is
moving at a speed between approximately 35 and 85
mph. In order for the speed control to engage, the
brakes cannot be applied, nor can the gear selector
be indicating the transmission is in Park or Neutral.
The speed control can be disengaged manually by:
²Stepping on the brake pedal
²Depressing the OFF switch
²Depressing the CANCEL switch.
The speed control can be disengaged also by any of
the following conditions:
²An indication of Park or Neutral
²The VSS signal increases at a rate of 10 mph
per second (indicates that the co-efficient of friction
between the road surface and tires is extremely low)
²Depressing the clutch pedal.
²Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
²The VSS signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
²If the actual speed is not within 20 mph of the
set speed
The previous disengagement conditions are pro-
grammed for added safety.
Once the speed control has been disengaged,
depressing the ACCEL switch restores the vehicle to
the target speed that was stored in the PCM's RAM.
NOTE: Depressing the OFF switch will erase the set
speed stored in the PCM's RAM.
If, while the speed control is engaged, the driver
wishes to increase vehicle speed, the PCM is pro-
grammed for an acceleration feature. With the
ACCEL switch held closed, the vehicle accelerates
slowly to the desired speed. The new target speed is
stored in the PCM's RAM when the ACCEL switch isreleased. The PCM also has a9tap-up9feature in
which vehicle speed increases at a rate of approxi-
mately 2 mph for each momentary switch activation
of the ACCEL switch.
The PCM also provides a means to decelerate with-
out disengaging speed control. To decelerate from an
existing recorded target speed, depress and hold the
COAST switch until the desired speed is reached.
Then release the switch. The ON, OFF switch oper-
ates two components: the PCM's ON, OFF input, and
the battery voltage to the brake switch, which powers
the speed control servo.
Multiplexing
The PCM sends out 5 volts through a fixed resistor
and monitors the voltage change between the fixed
resistor and the switches. If none of the switches are
depressed, the PCM will measure 5 volts at the sen-
sor point (open circuit). If a switch with no resistor is
closed, the PCM will measure 0 volts (grounded cir-
cuit). Now, if a resistor is added to a switch, then the
PCM will measure some voltage proportional to the
size of the resistor. By adding a different resistor to
each switch, the PCM will see a different voltage
depending on which switch is pushed.
Another resistor has been added to the 'at rest cir-
cuit' causing the PCM to never see 5 volts. This was
done for diagnostic purposes. If the switch circuit
should open (bad connection), then the PCM will see
the 5 volts and know the circuit is bad. The PCM will
then set an open circuit fault.
REMOVAL
WARNING: BEFORE BEGINNING ANY AIRBAG SYS-
TEM COMPONENT REMOVAL OR INSTALLATION,
REMOVE AND ISOLATE THE NEGATIVE (-) CABLE
FROM THE BATTERY. THIS IS THE ONLY SURE
WAY TO DISABLE THE AIRBAG SYSTEM. THEN
WAIT TWO MINUTES FOR SYSTEM CAPACITOR TO
DISCHARGE BEFORE FURTHER SYSTEM SERVICE.
FAILURE TO DO THIS COULD RESULT IN ACCIDEN-
TAL AIRBAG DEPLOYMENT AND POSSIBLE
INJURY.
(1) Disconnect and isolate negative battery cable.
(2) Remove airbag module. Refer to Group 8M,
Passive Restraint Systems.
(3) Remove electrical connector at switch.
(4) Remove switch-to-steering wheel mounting
screw (Fig. 7) .
(5) Remove switch.
INSTALLATION
(1) Install switch and mounting screw.
(2) Tighten screw to 1.5 N´m (15 in. lbs.) torque.
(3) Install electrical connector to switch.
WJSPEED CONTROL 8P - 7

CONDITION POSSIBLE CAUSES CORRECTION
3. Worn or incorrect gapped spark
plugs3. Clean plugs and set gap. (Refer to
8 - ELECTRICAL/IGNITION
CONTROL/SPARK PLUG -
CLEANING).
4. Dirt or water in fuel system 4. Clean system and replace fuel
filter
5. Faulty fuel pump 5. Install new fuel pump
6. Incorrect valve timing 6. Correct valve timing
7. Blown cylinder head gasket 7. Install new cylinder head gasket
8. Low compression 8. Test cylinder compression. (Refer
to 9 - ENGINE - DIAGNOSIS AND
TESTING).
9. Burned, warped, or pitted valves 9. Install/Reface valves as necessary
10. Plugged or restricted exhaust
system10. Install new parts as necessary
11. Faulty ignition coil rail 11. Test and replace, as necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL).
ENGINE STALLS OR ROUGH
IDLE1. Carbon build-up on throttle plate 1. Remove throttle body and
de-carbon. (Refer to 14 - FUEL
SYSTEM/FUEL INJECTION/
THROTTLE BODY - REMOVAL) for
correct procedure.
2. Engine idle speed too low 2. Check Idle Air Control circuit.
3. Worn or incorrectly gapped spark
plugs3. Replace or clean and re-gap spark
plugs. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING)
4. Faulty coil rail 4. Test and replace, if necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL)
5. Intake manifold vacuum leak 5. Inspect intake manifold gasket and
vacuum hoses. Replace if necessary.
(Refer to 9 - ENGINE/MANIFOLDS/
INTAKE MANIFOLD - DIAGNOSIS
AND TESTING).
ENGINE MISSES ON
ACCELERATION1. Worn or incorrectly gapped spark
plugs1. Replace spark plugs or clean and
set gap.
2. Spark plug cables defective or
crossed2. Replace spark plug cables.
3. Dirt in fuel system 3. Clean fuel system
4. Burned, warped or pitted valves 4. Install new valves
5. Faulty coil rail 5. Test and replace as necessary.
(Refer to 8 - ELECTRICAL/IGNITION
CONTROL/COIL RAIL - REMOVAL)
WJENGINE - 4.0L 9 - 5
ENGINE - 4.0L (Continued)

CONDITION POSSIBLE CAUSE CORRECTION
1. ENGINE MISSES ON
ACCELERATION1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG -
CLEANING).
2. Dirt in fuel system. 2. Clean fuel system.
3. Burned, warped or pitted valves. 3. Replcae as necessary.
4. Faulty coil. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION COIL -
REMOVAL).
1. ENGINE MISSES AT HIGH
SPEED1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG -
CLEANING).
2. Faulty coil. 2. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION COIL -
REMOVAL).
3. Dirt or water in fuel system. 3. Clean system and replace fuel filter.
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - MECHANICAL
CONDITION POSSIBLE CAUSES CORRECTIONS
NOISY VALVES 1. High or low oil level in crankcase. 1. (Refer to LUBRICATION &
MAINTENANCE/FLUID TYPES -
SPECIFICATIONS).
2. Thin or diluted oil. 2. Change oil and filter.
3. Low oil pressure. 3. Check oil pump, if Ok, check rod
and main bearings for excessive wear.
4. Dirt in lash adjusters. 4. Replace as necessary.
5. Worn rocker arms. 5. Replace as necessary.
6. Worn lash adjusters 6. Replace as necessary.
7. Worn valve guides. 7. (Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES &
SEATS - STANDARD PROCEDURE).
8. Excessive runout of valve seats
on valve faces.8. Service valves and valve seats.
(Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES &
SEATS - STANDARD PROCEDURE).
CONNECTING ROD NOISE 1. Insufficient oil supply. 1. (Refer to LUBRICATION &
MAINTENANCE/FLUID TYPES -
SPECIFICATIONS).
2. Low oil pressure. 2. Check oil pump, if Ok, check rod
and main bearings for excessive wear.
3. Thin or diluted oil. 3. Change oil and filter.
4. Excessive bearing clearance. 4. Replace as necessary.
5. Connecting rod journal out-of-
round.5. Service or replace crankshaft.
6. Misaligned connecting rods. 6. Replace bent connecting rods.
9 - 66 ENGINE - 4.7LWJ
ENGINE - 4.7L (Continued)

Normal calibration will be performed when sump
temperature is above 50 degrees F, or in the absence
of sump temperature data, after the first 10 minutes
of vehicle operation. Calibration of the pressure
transducer offset occurs each time the output shaft
speed falls below 200 RPM. Calibration shall be
repeated each 3 seconds the output shaft speed is
below 200 RPM. A 0.5 second pulse of 95% duty cycle
is applied to the governor pressure solenoid valve
and the transducer output is read during this pulse.
Averaging of the transducer signal is necessary to
reject electrical noise.
Under cold conditions (below 50 degrees F sump),
the governor pressure solenoid valve response may
be too slow to guarantee 0 psi during the 0.5 second
calibration pulse. Calibration pulses are continued
during this period, however the transducer output
valves are discarded. Transducer offset must be read
at key-on, under conditions which promote a stable
reading. This value is retained and becomes the off-
set during the9cold9period of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to
normal transmission line pressure. The outlet side of
the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to pro-
duce governor pressure. The average current sup-
plied to the solenoid controls governor pressure. One
amp current produces zero kPa/psi governor pres-
sure. Zero amps sets the maximum governor pres-
sure.
The powertrain control module (PCM) turns on the
trans control relay which supplies electrical power to
the solenoid valve. Operating voltage is 12 volts
(DC). The PCM controls the ground side of the sole-
noid using the governor pressure solenoid control cir-
cuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary
feedback to the PCM. This feedback is needed to ade-
quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the
solenoid valve through the governor body. It also
channels governor pressure from the solenoid valve
to the governor circuit. It is the solenoid valve that
develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conven-
tional governor can delay shifts, resulting in higherthan normal shift speeds and harsh shifts. The elec-
tronically controlled low temperature governor pres-
sure curve is higher than normal to make the
transmission shift at normal speeds and sooner. The
PCM uses a temperature sensor in the transmission
oil sump to determine when low temperature gover-
nor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased
computing power of the PCM and through access to
data on engine operating conditions provided by the
PCM that were not available with the previous
stand-alone electronic module. This facilitated the
development of a load adaptive shift strategy - the
ability to alter the shift schedule in response to vehi-
cle load condition. One manifestation of this capabil-
ity is grade9hunting9prevention - the ability of the
transmission logic to delay an upshift on a grade if
the engine does not have sufficient power to main-
tain speed in the higher gear. The 3-2 downshift and
the potential for hunting between gears occurs with a
heavily loaded vehicle or on steep grades. When
hunting occurs, it is very objectionable because shifts
are frequent and accompanied by large changes in
noise and acceleration.
WIDE OPEN THROTTLE OPERATION
In wide-open throttle (WOT) mode, adaptive mem-
ory in the PCM assures that up-shifts occur at the
preprogrammed optimum speed. WOT operation is
determined from the throttle position sensor, which
is also a part of the emission control system. The ini-
tial setting for the WOT upshift is below the opti-
mum engine speed. As WOT shifts are repeated, the
PCM learns the time required to complete the shifts
by comparing the engine speed when the shifts occur
to the optimum speed. After each shift, the PCM
adjusts the shift point until the optimum speed is
reached. The PCM also considers vehicle loading,
grade and engine performance changes due to high
altitude in determining when to make WOT shifts. It
does this by measuring vehicle and engine accelera-
tion and then factoring in the shift time.
TRANSFER CASE LOW RANGE OPERATION
On four-wheel drive vehicles operating in low
range, the engine can accelerate to its peak more
rapidly than in Normal range, resulting in delayed
shifts and undesirable engine9flare.9The low range
governor pressure curve is also higher than normal
to initiate upshifts sooner. The PCM compares elec-
tronic vehicle speed signal used by the speedometer
to the transmission output shaft speed signal to
determine when the transfer case is in low range.
21 - 66 AUTOMATIC TRANSMISSION - 42REWJ
ELECTRONIC GOVERNOR (Continued)

2-3 SHIFT VALVE
The 2-3 shift valve mechanism (Fig. 269) consists
of the 2-3 shift valve, governor plug and spring, and
a throttle plug. After the 1-2 shift valve has com-
pleted its operation and applied the front band, line
pressure is directed to the 2-3 shift valve through theconnecting passages from the 1-2 shift valve. The line
pressure will then dead±end at land #2 until the 2-3
valve is ready to make its shift. Now that the vehicle
is in motion and under acceleration, there is throttle
pressure being applied to the spring side of the valve
and between lands #3 and #4.
Fig. 269 2-3 Shift Valve-Before Shift
WJAUTOMATIC TRANSMISSION - 42RE 21 - 147
VALVE BODY (Continued)

Diagnosis of these problems should always begin
by checking the easily accessible variables: fluid level
and condition, gearshift cable adjustment. Then per-
form a road test to determine if the problem has been
corrected or if more diagnosis is necessary. If the
problem persists after the preliminary tests and cor-
rections are completed, hydraulic pressure checks
should be performed.
DIAGNOSIS AND TESTING - PRELIMINARY
Two basic procedures are required. One procedure for
vehicles that are drivable and an alternate procedure for
disabled vehicles (will not back up or move forward).
VEHICLE IS DRIVABLE
(1) Check for transmission fault codes using DRBt
scan tool.
(2) Check fluid level and condition.
(3) Adjust gearshift cable if complaint was based
on delayed, erratic, or harsh shifts.
(4) Road test and note how transmission upshifts,
downshifts, and engages.
(5) Perform stall test if complaint is based on slug-
gish acceleration. Or, if abnormal throttle opening is
needed to maintain normal speeds with a properly
tuned engine.
(6) Perform hydraulic pressure test if shift prob-
lems were noted during road test.
(7)
Perform air-pressure test to check clutch operation.
VEHICLE IS DISABLED
(1) Check fluid level and condition.
(2)
Check for broken or disconnected gearshift cable.
(3) Check for cracked, leaking cooler lines, or loose
or missing pressure-port plugs.(4) Raise and support vehicle on safety stands,
start engine, shift transmission into gear, and note
following:
(a) If propeller shaft turns but wheels do not,
problem is with differential or axle shafts.
(b) If propeller shaft does not turn and transmis-
sion is noisy, stop engine. Remove oil pan, and
check for debris. If pan is clear, remove transmis-
sion and check for damaged driveplate, converter,
oil pump, or input shaft.
(c) If propeller shaft does not turn and transmis-
sion is not noisy, perform hydraulic-pressure test to
determine if problem is hydraulic or mechanical.
DIAGNOSIS AND TESTING - ROAD TESTING
Before road testing, be sure the fluid level and con-
trol cable adjustments have been checked and
adjusted if necessary. Verify that all diagnostic trou-
ble codes have been resolved.
Observe engine performance during the road test.
A poorly tuned engine will not allow accurate analy-
sis of transmission operation.
Operate the transmission in all gear ranges. Check
for shift variations and engine flare which indicates
slippage. Note if shifts are harsh, spongy, delayed,
early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means
clutch, overrunning clutch, or line presure problems.
A slipping clutch can often be determined by com-
paring which internal units are applied in the vari-
ous gear ranges. The Clutch Application chart
provides a basis for analyzing road test results.
CLUTCH APPLICATION CHART
SLP UD OD R 2C 4C L/R OVERRUNNING
P±PARKON
R±REVERSEON ON
N-NEUTRALON
D±OVERDRIVE
FIRSTON ON* ON
SECONDON ON
SECOND PRIMEON ON
THIRDON ON
FOURTHON ON
FIFTHON ON
LIMP-INON ON
2±FIRSTON ON* ON
SECONDON ON
LIMP-INON ON
1±LOWON ON ON
*L/R clutch is on only with the output shaft speed below 150 rpm.
21 - 180 AUTOMATIC TRANSMISSION - 545RFEWJ
AUTOMATIC TRANSMISSION - 545RFE (Continued)

TIRES
DESCRIPTION
DESCRIPTION - TIRES
Tires are designed and engineered for each specific
vehicle. They provide the best overall performance
for normal operation. The ride and handling charac-
teristics match the vehicle's requirements. With
proper care they will give excellent reliability, trac-
tion, skid resistance, and tread life.
Driving habits have more effect on tire life than
any other factor. Careful drivers will obtain in most
cases, much greater mileage than severe use or care-
less drivers. A few of the driving habits which will
shorten the life of any tire are:
²Rapid acceleration
²Severe brake applications
²High speed driving
²Excessive speeds on turns
²Striking curbs and other obstacles
Radial-ply tires are more prone to irregular tread
wear. It is important to follow the tire rotation inter-
val shown in the section on Tire Rotation.(Refer to 22
- TIRES/WHEELS - STANDARD PROCEDURE),
This will help to achieve a greater tread life.
TIRE IDENTIFICATION
Tire type, size, aspect ratio and speed rating are
encoded in the letters and numbers imprinted on the
side wall of the tire. Refer to the chart to decipher
the tire identification code (Fig. 12).
Performance tires have a speed rating letter after
the aspect ratio number. The speed rating is not
always printed on the tire sidewall. These ratings
are:
²Qup to 100 mph
²Sup to 112 mph
²Tup to 118 mph
²Uup to 124 mph
²Hup to 130 mph
²Vup to 149 mph
²Zmore than 149 mph (consult the tire manu-
facturer for the specific speed rating)
An All Season type tire will have eitherM+S,M
&SorM±S(indicating mud and snow traction)
imprinted on the side wall.
TIRE CHAINS
Tire snow chains may be used oncertainmodels.
Refer to the Owner's Manual for more information.
DESCRIPTION - RADIAL±PLY TIRES
Radial-ply tires improve handling, tread life and
ride quality, and decrease rolling resistance.Radial-ply tires must always be used in sets of
four. Under no circumstances should they be used on
the front only. They may be mixed with temporary
spare tires when necessary. A maximum speed of 50
MPH is recommended while a temporary spare is in
use.
Radial-ply tires have the same load-carrying capac-
ity as other types of tires of the same size. They also
use the same recommended inflation pressures.
The use of oversized tires, either in the front or
rear of the vehicle, can cause vehicle drive train fail-
ure. This could also cause inaccurate wheel speed
signals when the vehicle is equipped with Anti-Lock
Brakes.
The use of tires from different manufactures on the
same vehicle is NOT recommended. The proper tire
pressure should be maintained on all four tires.
DESCRIPTION - TIRE INFLATION PRESSURES
Under inflation will cause rapid shoulder wear, tire
flexing, and possible tire failure (Fig. 13).
Over inflation will cause rapid center wear and
loss of the tire's ability to cushion shocks (Fig. 14).
Improper inflation can cause:
²Uneven wear patterns
²Reduced tread life
²Reduced fuel economy
Fig. 12 Tire Identification
22 - 6 TIRES/WHEELSWJ

DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - PRESSURE
GAUGES
A quality air pressure gauge is recommended to
check tire pressure. After checking the air pressure,
replace valve cap finger tight.
DIAGNOSIS AND TESTING - TREAD WEAR
INDICATORS
Tread wear indicators are molded into the bottom
of the tread grooves. When tread depth is 1.6 mm
(1/16 in.), the tread wear indicators will appear as a
13 mm (1/2 in.) band (Fig. 15).
Tire replacement is necessary when indicators
appear in two or more grooves or if localized balding
occurs.
DIAGNOSIS AND TESTING - TIRE WEAR
PATTERNS
Under inflation will cause wear on the shoulders of
tire. Over inflation will cause wear at the center of
tire.
Excessive camber causes the tire to run at an
angle to the road. One side of tread is then worn
more than the other (Fig. 16).
Excessive toe-in or toe-out causes wear on the
tread edges and a feathered effect across the tread
(Fig. 16).
DIAGNOSIS AND TESTING - TIRE NOISE OR
VIBRATION
Radial-ply tires are sensitive to force impulses
caused by improper mounting, vibration, wheel
defects, or possibly tire imbalance.
To find out if tires are causing the noise or vibra-
tion, drive the vehicle over a smooth road at varying
speeds. Note the noise level during acceleration and
deceleration. The engine, differential and exhaust
noises will change as speed varies, while the tire
noise will usually remain constant.
STANDARD PROCEDURE - REPAIRING LEAKS
For proper repairing, a radial tire must be removed
from the wheel. Repairs should only be made if the
defect, or puncture, is in the tread area (Fig. 17). The
tire should be replaced if the puncture is located in
the sidewall.
Deflate tire completely before removing the tire
from the wheel. Use lubrication such as a mild soap
solution when dismounting or mounting tire. Use
tools free of burrs or sharp edges which could dam-
age the tire or wheel rim.
Before mounting tire on wheel, make sure all rust
is removed from the rim bead and repaint if neces-
sary.
Install wheel on vehicle, and tighten to proper
torque specification (Refer to 22 - TIRES/WHEELS/
WHEELS - SPECIFICATIONS).
Fig. 15 Tread Wear Indicators
1 - TREAD ACCEPTABLE
2 - TREAD UNACCEPTABLE
3 - WEAR INDICATOR
22 - 8 TIRES/WHEELSWJ