Rpm JEEP CHEROKEE 1995 Service Repair Manual

JUMP STARTING, TOWING AND HOISTING
INDEX
page page
Four-Wheel-Drive Vehicle Towing............. 12
Ground Clearance and Ramp Angle............ 11
Hoisting Recommendations.................. 10
Jump Starting Procedure..................... 9Towing Recommendations................... 10
Towing When Keys Are Not Available.......... 13
Two-Wheel-Drive Vehicle TowingÐXJ.......... 11
JUMP STARTING PROCEDURE
WARNING: DO NOT ATTEMPT TO PUSH OR TOW A
VEHICLE TO START THE ENGINE. UNBURNED
FUEL COULD ENTER THE EXHAUST CATALYTIC
CONVERTER AND IGNITE AFTER THE ENGINE IS
STARTED. THIS COULD CAUSE THE CONVERTER
TO OVERHEAT AND RUPTURE.
WARNING: REVIEW ALL SAFETY PRECAUTIONS
AND WARNINGS IN GROUP 8A, BATTERY/START-
ING/CHARGING SYSTEMS DIAGNOSTICS.
DO NOT JUMP START A FROZEN BATTERY, PER-
SONAL INJURY CAN RESULT.
DO NOT JUMP START WHEN MAINTENANCE
FREE BATTERY INDICATOR DOT IS YELLOW OR
BRIGHT COLOR.
DO NOT JUMP START A VEHICLE WHEN THE
BATTERY FLUID IS BELOW THE TOP OF LEAD
PLATES.
DO NOT ALLOW JUMPER CABLE CLAMPS TO
TOUCH EACH OTHER WHEN CONNECTED TO A
BOOSTER SOURCE.
DO NOT USE OPEN FLAME NEAR BATTERY.
REMOVE METALLIC JEWELRY WORN ON HANDS
OR WRISTS TO AVOID INJURY BY ACCIDENTAL
ARCING OF BATTERY CURRENT.
WHEN USING A HIGH OUTPUT BOOSTING DE-
VICE, DO NOT ALLOW BATTERY VOLTAGE TO EX-
CEED 16 VOLTS. REFER TO INSTRUCTIONS
PROVIDED WITH DEVICE BEING USED.
CAUTION: When using another vehicle as a
booster, do not allow vehicles to touch. Electrical
systems can be damaged on either vehicle.
TO JUMP START A DISABLED VEHICLE:
(1) Raise hood on disabled vehicle and visually in-
spect engine compartment for:
²Battery cable clamp condition, clean if necessary.
²Frozen battery.
²Yellow or bright color test indicator, if equipped.
²Low battery fluid level.
²Generator drive belt condition and tension.²Fuel fumes or leakage, correct if necessary.
CAUTION: If the cause of starting problem on dis-
abled vehicle is severe, damage to booster vehicle
charging system can result.
(2) When using another vehicle as a booster
source, turn off all accessories, place gear selector in
park or neutral, set park brake and operate engine at
1200 rpm.
(3) On disabled vehicle, place gear selector in park
or neutral and set park brake. Turn off all accesso-
ries.
(4) Connect jumper cables to booster battery. RED
clamp to positive terminal (+). BLACK clamp to neg-
ative terminal (-). DO NOT allow clamps at opposite
end of cables to touch, electrical arc will result. Re-
view all warnings in this procedure.
(5) On disabled vehicle, connect RED jumper cable
clamp to positive (+) terminal. Connect BLACK
jumper cable clamp to engine ground as close to the
ground cable attaching point as possible (Fig. 1).
Fig. 1 Jumper Cable ConnectionsÐTypical
JLUBRICATION AND MAINTENANCE 0 - 9

produce a condition similar to grab as the tire loses
and recovers traction.
Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation.
A tire with internal damage such as a severe bruise
or ply separation can cause vibration and pull. The
pull will be magnified when braking.
DIAGNOSING PARKING BRAKE MALFUNCTIONS
Adjustment Mechanism
Parking brake adjustment is controlled by a ca-
ble tensioner mechanism. The cable tensioner,
once adjusted at the factory, will not need further
attention under normal circumstances. There are
only two instances when adjustment is required.
The first is when a new tensioner, or cables have
been installed. And the second, is when the ten-
sioner and cables are disconnected for access to
other brake components.
Parking Brake Switch And Warning Light Illumination
The parking brake switch on the lever, or foot
pedal, is in circuit with the red warning light. The
switch will illuminate the red light only when the
parking brakes are applied. If the light remains on
after parking brake release, the switch or wires are
faulty, or cable tensioner adjustment is incorrect.
If the red light comes on while the vehicle is in mo-
tion and brake pedal height decreases, a fault has oc-
curred in the front or rear brake hydraulic system.
Parking Brake problem Causes
In most cases, the actual cause of an improperly
functioning parking brake (too loose/too tight/wont
hold), can be traced to a drum brake component.
The leading cause of improper parking brake
operation, is excessive clearance between the
brakeshoes and the drum surface. Excessive
clearance is a result of: lining and/or drum
wear; oversize drums; or inoperative shoe ad-
juster components.
Excessive parking brake lever travel (sometimes de-
scribed as a loose lever or too loose condition), is the re-
sult of worn brakeshoes/drums, improper brakeshoe
adjustment, or incorrectly assembled brake parts.
A ``too loose'' condition can also be caused by inop-
erative brakeshoe adjusters. If the adjusters are mis-
assembled, they will not function. In addition, since
the adjuster mechanism only works during reverse
stops, it is important that complete stops be made.
The adjuster mechanism does not operate when roll-
ing stops are made in reverse. The vehicle must be
brought to a complete halt before the adjuster lever
will turn the adjuster screw.
A condition where the parking brakes do not hold, will
most probably be due to a wheel brake component.
Items to look for when diagnosing a parking brake
problem, are:
²rear brakeshoe wear or adjuster problem
²rear brake drum wear
²brake drums machined beyond allowable diameter
(oversize)
²parking brake front cable not secured to lever
²parking brake rear cable seized
²parking brake strut reversed
²parking brake strut not seated in both shoes
²parking brake lever not seated in secondary shoe
²parking brake lever or brakeshoe bind on support
plate
²brakeshoes reversed
²adjuster screws seized
²adjuster screws reversed
²holddown or return springs misassembled or lack
tension
²wheel cylinder pistons seized
Brake drums that are machined oversize are diffi-
cult to identify without inspection. If oversize drums
are suspected, diameter of the braking surface will
have to be checked with an accurate drum gauge.
Oversize drums will cause low brake pedal and lack
of parking brake holding ability.
Improper parking brake strut and lever installation
will result in unsatisfactory parking brake operation.
Intermixing the adjuster screws will cause drag, bind
and pull along with poor parking brake operation.
Parking brake adjustment and parts replacement pro-
cedures are described in the Parking Brake section.
MASTER CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose
connections. Hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neu-
tral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure.
(a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away,
master cylinder is faulty due to internal leakage.
Overhaul or replace cylinder.
(5) Start engine and note pedal action.
(a) If pedal falls away slightly under light foot
pressure then holds firm, proceed to step (6).
(b) If no pedal action is discernible, or hard pedal
is noted, power booster or vacuum check valve is
faulty. Install known good check valve and repeat
steps (2) through (5).
(6) Rebuild booster vacuum reserve as follows: Re-
lease brake pedal. Increase engine speed to 1500
rpm, close throttle and immediately turn off ignition.
5 - 8 SERVICE BRAKE DIAGNOSISJ

DIAGNOSIS
INDEX
page page
DRB Scan Tool............................ 5
On-Board Diagnostics (OBD).................. 4Preliminary Checks......................... 5
ON-BOARD DIAGNOSTICS (OBD)
FOR CERTAIN COOLING SYSTEM
COMPONENTS
The powertrain control module (PCM) has been
programmed to monitor the certain following cooling
system components:
²If the engine has remained cool for too long a pe-
riod, such as with a stuck open thermostat, a Diag-
nostic Trouble Code (DTC) number 17 can be
observed at the malfunction indicator lamp. This
lamp is displayed on the instrument panel as the
CHECK ENGINE lamp (Figs. 5 or 6).
²If an open or shorted condition has developed in
the relay circuit controlling the electric radiator fan,
a Diagnostic Trouble Code (DTC) number 35 can be
observed at the CHECK ENGINE lamp (XJ models
only).
If the problem is sensed in a monitored circuit of-
ten enough to indicate an actual problem, a DTC is
stored. The DTC will be stored in the PCM memory
for eventual display to the service technician. If theproblem is repaired or ceases to exist, the PCM can-
cels the DTC after 51 engine starts.
Certain criteria must be met for a DTC to be en-
tered into PCM memory. The criteria may be a spe-
cific range of engine rpm, engine temperature and/or
input voltage to the PCM.
A DTC indicates that the PCM has recognized an
abnormal signal in a circuit or the system. A DTC
may indicate the result of a failure, but never iden-
tify the failed component directly.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a mal-
function has occurred. Refer to On-Board Diagnostics
(OBD) in Group 14, Fuel Systems for additional DTC
information.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored Diagnostic Trouble Code (DTC) can be dis-
played by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the malfunction
indicator lamp. This lamp is displayed on the instru-
ment panel as the CHECK ENGINE lamp (Figs. 5 or
6).
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool. The DRB
connects to the data link connector in the engine
compartment (Figs. 7 or 8). For operation of the
DRB, refer to the appropriate Powertrain Diagnostic
Procedures service manual.
Fig. 5 Check Engine LampÐXJ ModelsÐTypical
Fig. 6 Check Engine LampÐYJ ModelsÐTypical
7 - 4 COOLING SYSTEM DIAGNOSISJ

CAUTION: Do not operate the engine with a spark
plug shorted for more than a minute. The catalytic
converter may be damaged.
Isolate the compression leak by shorting each
spark plug to the cylinder block. The gauge pointer
should stop or decrease vibration when spark plug
for leaking cylinder is shorted. This happens because
of the absence of combustion pressure.
COMBUSTION LEAKAGE TEST (WITHOUT
PRESSURE TESTER)
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
Drain sufficient coolant to allow for thermostat re-
moval. Refer to Thermostat Replacement. Disconnect
the water pump drive belt.
Disconnect the upper radiator hose from the ther-
mostat housing. Remove the housing and thermostat.
Install the thermostat housing.
Add coolant to the radiator to bring the level to
within 6.3 mm (1/4 in) of the top of the thermostat
housing.
CAUTION: Avoid overheating. Do not operate the
engine for an excessive period of time. Open the
draincock immediately after the test to eliminate
boil over of coolant.
Start the engine and accelerate rapidly three times
(to approximately 3000 rpm) while observing the
coolant. If internal engine combustion gases are leak-
ing into the cooling system, bubbles will appear in
the coolant. If bubbles do not appear, there is no in-
ternal combustion gas leakage.
COOLANT RESERVE/OVERFLOW SYSTEM
The system works along with the radiator pressure
cap. This is done by using thermal expansion and
contraction of the coolant to keep the coolant free of
trapped air. It provides:
²A volume for coolant expansion and contraction.
²A convenient and safe method for checking/adjust-
ing coolant level at atmospheric pressure. This is
done without removing the radiator pressure cap.
²Some reserve coolant to the radiator to cover mi-
nor leaks and evaporation or boiling losses.
As the engine cools, a vacuum is formed in the
cooling system of both the radiator and engine. Cool-ant will then be drawn from the coolant tank and re-
turned to a proper level in the radiator.
The coolant reserve/overflow system consists of a
radiator mounted pressurized cap, a plastic reserve/
overflow tank (Figs. 22, 23 or 24), a tube (hose) con-
necting the radiator and tank, and an overflow tube
on the side of the tank.
Fig. 22 Reserve/Overflow TankÐYJ Models
Fig. 23 Reserve/Overflow TankÐXJ ModelsÐExcept
Right Hand Drive
7 - 24 COOLING SYSTEM SERVICE PROCEDURESJ

VISCOUS FAN DRIVE
DESCRIPTION AND OPERATION
Also refer to the previous section on Cooling Sys-
tem Fans.
The thermal viscous fan drive (Fig. 38 or 39) is a
silicone-fluid-filled coupling used to connect the fan
blades to either the engine or the water pump shaft.
The coupling allows the fan to be driven in a normal
manner. This is done at low engine speeds while lim-
iting the top speed of the fan to a predetermined
maximum level at higher engine speeds.
A thermostatic bimetallic spring coil is located on
the front face of the viscous fan drive unit (a typical
viscous unit is shown in figure 40). This spring coil
reacts to the temperature of the radiator 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 re-
gardless of engine speed.
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 bi-
metallic 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 re-
acts and the fan speed is reduced to the previous dis-
engaged speed.
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 be-
cause 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.
NOISE
It is normal for fan noise to be louder (roar-
ing) when:
²The underhood temperature is above the engage-
ment point for the viscous drive coupling. This may
occur when ambient (outside air temperature) is very
high.
²Engine loads and temperatures are high such as
when towing a trailer.
²Cool silicone fluid within the fan drive unit is be-
ing redistributed back to its normal disengaged
(warm) position. This can occur during the first 15
seconds to one minute after engine start-up on a cold
engine.
LEAKS
Viscous fan drive operation is not affected by small
oil stains near the drive bearing. If leakage appears
excessive, replace the fan drive unit.
TESTING
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.
Fig. 40 Typical Viscous Fan Drive
7 - 34 COOLING SYSTEM SERVICE PROCEDURESJ

(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 DI-
RECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR FAN. DO
NOT WEAR LOOSE CLOTHING.
(6) Start the engine and operate at 2400 rpm.
Within ten minutes the air temperature (indicated on
the dial thermometer) should be up to 88É C (190É F).
Fan driveengagementshould have started to occur
at between 74É to 82É C (165É to 180É 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 88É C (190É
F), remove the plastic sheet. Fan drivedisengage-
mentshould have started to occur at between 57É to
79É C (135É to 175É F). A definitedecreaseof fan
flow noise (roaring) should be noticed. If not, replace
the defective viscous fan drive unit.
VISCOUS FAN DRIVE REMOVAL/INSTALLATION
Refer to the previous section on Cooling System
Fan for removal and installation procedures of the
viscous drive unit.
Viscous Fan Drive Fluid Pump Out Require-
ment:After installing anewviscous fan drive, bring
the engine speed up to approximately 2000 rpm and
hold for approximately two minutes. This will ensure
proper fluid distribution within the drive.
AUXILIARY ELECTRIC COOLING FANÐXJ MODELS
WITH 4.0L 6-CYLINDER ENGINE
OPERATION
XJ models equipped with a 4.0L 6-cylinder engine
may also have an auxiliary electrical cooling fan.
This is with models that have air conditioning and/or
heavy duty cooling. The fan is controlled by the cool-
ing fan relay, which is located in the power distribu-
tion center (PDC). For the location of relay within
the PDC (Fig. 41), refer to the label on PDC cover.
When coolant temperature is above 88ÉC (190ÉF),
the powertrain control module (PCM) provides a
ground path for the fan relay. This ground is pro-
vided through pin/connector #31 of the PCM 60-way
connector. Battery voltage is then applied to the fan
through the relay. When coolant temperature is be-
low 88ÉC (190ÉF), the PCM opens the ground path to
the relay. This will prevent the cooling fan from be-
ing energized.
Whenever the air conditioning is operated, the
PCM engages the auxiliary cooling fan. It provides aground path to the cooling fan relay. This ground is
provided through pin/connector #31 of the PCM 60-
way connector.
DIAGNOSIS AND RELAY TESTING
The powertrain control module (PCM) will enter a
diagnostic trouble code (DTC) number 35 in memory
if it detects a problem in the auxiliary cooling fan re-
lay or circuit. This will be read as a flashing signal
at the instrument panel mounted Malfunction Indica-
tor Lamp (displayed on the instrument panel as the
CHECK ENGINE lampÐfigure 42). Refer to On-
Board Diagnostics in Group 14, Fuel Systems for in-
formation on accessing a DTC.
The DTC can also be accessed through the DRB
scan tool. Refer to the appropriate Powertrain Diag-
Fig. 41 PDCÐXJ Models
Fig. 42 Check Engine LampÐXJ ModelsÐTypical
JCOOLING SYSTEM SERVICE PROCEDURES 7 - 35

(5) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to generator battery output ter-
minal.
(6) Connect negative lead of test voltmeter to a
good ground.
(7) Connect an engine tachometer, then connect
battery negative cable to battery.
(8) Connect a variable carbon pile rheostat be-
tween battery terminals. Be sure carbon pile is in
OPEN or OFF position before connecting leads. See
Load Test in this group for instructions.
(9) Connect one end of a jumper wire to ground
and with other end probe green K20 field wire at
back of generator (Fig. 3). This will generate a DTC.
CAUTION: Do not connect green/orange A142 field
wire to ground. Refer to Group 8W - Wiring Dia-
grams for more information.TEST
(1) Start engine. Immediately after starting, re-
duce engine speed to idle.
(2) Adjust carbon pile and engine speed in incre-
ments until a speed of 1250 rpm and voltmeter read-
ing of 15 volts is obtained.
CAUTION: Do not allow voltage meter to read above
16 volts.
(3) The ammeter reading must be within limits
shown in Generator Output Voltage Specifications.
RESULTS
(1) If reading is less than specified and generator
output wire resistance is not excessive, generator
should be replaced. Refer to Group 8B - Battery/
Starter/Generator Service.
CHARGING SYSTEM DIAGNOSIS
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 19

On the 4.0L 6-cylinder engine, the ignition coil is
mounted to a bracket on the side of the engine (to
the front of the distributor) (Fig. 11).
For component testing, refer to the Diagnostics/Ser-
vice Procedures section of this group.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
ENGINE COOLANT TEMPERATURE SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
POWERTRAIN CONTROL MODULE (PCM)
The PCM was formerly referred to as the SBEC or
engine controller. On XJ models, the PCM is located
in the engine compartment next to the air cleaner
(Fig. 12). On YJ models, the PCM is located in the
engine compartment behind the windshield washer
fluid reservoir (Fig. 13).
The ignition system is controlled by the PCM.
Base ignition timing by rotation of distributor
is not adjustable.The PCM opens and closes the ig-
nition coil ground circuit to operate the ignition coil.
This is done to adjust ignition timing, both initial
(base) and advance, for changing engine operating
conditions.The amount of electronic spark advance provided
by the PCM is determined by five input factors: En-
gine coolant temperature, engine rpm, intake mani-
fold air temperature, intake manifold absolute
pressure and throttle position.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
For PCM diagnostics, refer to the appropriate Pow-
ertrain Diagnostic Procedures service manual for op-
eration of the DRB scan tool.
THROTTLE POSITION SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
OXYGEN (O2S) SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
Fig. 11 Ignition CoilÐTypical
Fig. 12 PCM LocationÐXJ Models
Fig. 13 PCM LocationÐYJ Models
JIGNITION SYSTEMS 8D - 5

TACHOMETER
The tachometer gives an indication of engine speed
in Revolutions-Per-Minute (RPM). With the engine
running, the tachometer receives an engine speed
pulse signal from the Powertrain Control Module
(PCM). An electronic integrated circuit contained
within the tachometer reads and analyzes the pulse
signal. It then adjusts the ground path resistance of
one electromagnet in the gauge to control needle
movement. Frequency values for the pulse signal are
shown in a chart in Specifications.
TRIP ODOMETER
The trip odometer is driven by the same electronic
integrated circuit as the speedometer/odometer. How-
ever, by depressing the trip odometer reset knob on
the face of the speedometer, the trip odometer can be
reset to zero. The trip odometer is serviced only as a
part of the speedometer/odometer gauge assembly.
VOLTMETER
The voltmeter is connected in parallel with the bat-
tery. With the ignition switch ON, the voltmeter in-
dicates battery or generator output voltage,
whichever is greater.
INDICATOR LAMPS
Indicator lamps are located in two areas within the
cluster. Each of these areas is served by a separate
printed circuit and cluster connector. Those lamps in
the gauge area of the cluster share the gauge area
printed circuit and cluster connector A. Those lamps
in the tell-tale area of the cluster use the tell-tale
printed circuit and cluster (tell-tale) connector B.
Up to ten indicator lamps can be found in the tell-
tale area of the cluster. These lamps are arranged in
five stacked rows with two lamps in each row, located
to the driver's side of the main cluster.
ANTI-LOCK BRAKE SYSTEM LAMP
The Anti-Lock Brake System (ABS) lamp is
switched to ground by the ABS module. The module
lights the lamp when the ignition switch is turned to
the START position as a bulb test. The lamp will
stay on for 3 to 5 seconds after vehicle start-up to in-
dicate a system self-test is in process. If the lamp re-
mains on after start-up, or comes on and stays on
while driving, it may indicate that the ABS module
has detected a system malfunction or that the system
has become inoperative. Refer to Group 5 - Brakes
for more information.
BRAKE WARNING LAMP
The brake warning lamp warns the driver that the
parking brake is applied or that the pressures in the
two halves of the split brake hydraulic system are
unequal. With the ignition switch turned ON, batteryvoltage is supplied to one side of the indicator bulb. A
ground path for the bulb is provided by 3 switches.
The bulb will light when:
²the brake warning switch is closed (indicating un-
equal brake system hydraulic pressures possibly due
to brake fluid leakage)
²the ignition switch is in the START position (bulb
test)
²the parking brake switch is closed (parking brake
is applied).
Refer to Group 5 - Brakes for more information.
COOLANT TEMPERATURE WARNING LAMP
The coolant temperature warning lamp lights
whenever engine coolant temperature is too high.
Battery voltage is supplied to one side of the indica-
tor bulb when the ignition switch is turned ON. The
normally open coolant temperature switch is con-
nected to the other side of the bulb. When coolant
temperature is too high, the switch closes. This pro-
vides a ground path for the indicator bulb, which
causes it to light. The lamp is also grounded and
should light with the ignition switch in the START
position as a bulb test.
FOUR-WHEEL DRIVE INDICATOR LAMPS
PART TIME
On vehicles with Command-Trac 4WD, the Part
Time lamp lights when the transfer case is engaged
in the 4H or 4L position. On vehicles with Selec-Trac
4WD, the Part Time lamp lights when the transfer
case is engaged in the4X4PARTTIME or 4 LO po-
sition. Voltage is supplied to one side of the indicator
bulb. A switch in the transfer case is connected to the
other side of the indicator bulb. When the switch is
closed, a path to ground is provided and the indicator
bulb lights.
FULL TIME
The Full Time lamp is only operational on vehicles
equipped with Selec-Trac 4WD. The Full Time lamp
lights when the transfer case is engaged in the4X4
Full Time position. Voltage is supplied to one side of
the indicator bulb. A switch in the transfer case is
connected to the other side of the indicator bulb.
When the switch is closed, a path to ground is pro-
vided and the indicator bulb lights.
GENERATOR WARNING LAMP
The generator warning lamp lights with the igni-
tion switch turned to ON, but should go out when-
ever the engine is running. If the lamp comes on and
stays on while the engine is running, it indicates
that a charging system malfunction exists. One side
of the bulb is connected to ignition-switched battery
feed. The other side of the bulb is switched to ground
by the Powertrain Control Module (PCM).
JINSTRUMENT PANEL AND GAUGESÐXJ 8E - 3

The gauge needle moves as the movable permanent
magnet aligns itself to the changing magnetic fields
created around it by the electromagnets.
COOLANT TEMPERATURE GAUGE
The coolant temperature gauge gives an indication
of engine coolant temperature. The coolant tempera-
ture sending unit is a thermistor that changes elec-
trical resistance with changes in engine coolant
temperature. High sending unit resistance causes
low coolant temperature readings. Low resistance
causes high coolant temperature readings. Sending
unit resistance values are shown in a chart in Spec-
ifications.
FUEL GAUGE
The fuel gauge gives an indication of the level of
fuel in the fuel tank. The fuel gauge sending unit has
a float attached to a swing-arm in the fuel tank. The
float moves up or down within the fuel tank as fuel
level changes. As the float moves, an electrical con-
tact on the swing-arm wipes across a resistor coil,
which changes sending unit resistance. High sending
unit resistance causes high fuel level readings. Low
resistance causes low fuel level readings. Sending
unit resistance values are shown in a chart in Spec-
ifications.
OIL PRESSURE GAUGE
The oil pressure gauge gives an indication of en-
gine oil pressure. The combination oil pressure send-
ing unit contains a flexible diaphragm. The
diaphragm moves in response to changes in engine
oil pressure. As the diaphragm moves, sending unit
resistance increases or decreases. High resistance on
the gauge side of the sending unit causes high oil
pressure readings. Low resistance causes low oil
pressure readings. Sending unit resistance values are
shown in a chart in Specifications.
SPEEDOMETER/ODOMETER
The speedometer/odometer give an indication of ve-
hicle speed and travel distance. The speedometer re-
ceives a vehicle speed pulse signal from the Vehicle
Speed Sensor (VSS). An electronic integrated circuit
contained within the speedometer reads and analyzes
the pulse signal. It then adjusts the ground path re-
sistance of one electromagnet in the gauge to control
needle movement. It also sends signals to an electric
stepper motor to control movement of the odometer
number rolls. Frequency values for the pulse signal
are shown in a chart in Specifications.
The VSS is mounted to an adapter near the trans-
fer case output shaft. The sensor is driven through
the adapter by a speedometer pinion gear. The
adapter and pinion vary with transmission, axle ratio
and tire size. Refer to Group 21 - Transmission and
Transfer Case for more information.
TACHOMETER
The tachometer gives an indication of engine speed
in Revolutions-Per-Minute (RPM). With the engine
running, the tachometer receives an engine speed
pulse signal from the Powertrain Control Module
(PCM). An electronic integrated circuit contained
within the tachometer reads and analyzes the pulse
signal. It then adjusts the ground path resistance of
one electromagnet in the gauge to control needle
movement. Frequency values for the pulse signal are
shown in a chart in Specifications.
TRIP ODOMETER
The trip odometer is driven by the same electronic
integrated circuit as the speedometer/odometer. How-
ever, by depressing the trip odometer reset knob on
the face of the speedometer, the trip odometer can be
reset to zero. The trip odometer is serviced only as a
part of the speedometer/odometer gauge assembly.
VOLTMETER
The voltmeter is connected in parallel with the bat-
tery. With the ignition switch ON, the voltmeter in-
dicates battery or generator output voltage,
whichever is greater.
INDICATOR LAMPS
All indicator lamps, except the four-wheel drive in-
dicator, are located in the main cluster tell-tale area
above the steering column opening. Each of the
lamps is served by the main cluster printed circuit
and cluster connector. The four-wheel drive indicator
lamp is located in the gauge package cluster and is
served by the gauge package printed circuit and clus-
ter connector.
Up to eleven indicator lamps can be found in the
tell-tale area of the main cluster. These lamps are ar-
ranged in two rows, with six lamps in the upper row
and five lamps in the lower row.
ANTI-LOCK BRAKE SYSTEM LAMP
The Anti-Lock Brake System (ABS) lamp is
switched to ground by the ABS module. The module
lights the lamp when the ignition switch is turned to
the START position as a bulb test. The lamp will
stay on for 3 to 5 seconds after vehicle start-up to in-
dicate a system self-test is in process. If the lamp re-
mains on after start-up, or comes on and stays on
while driving, it may indicate that the ABS module
has detected a system malfunction or that the system
has become inoperative. Refer to Group 5 - Brakes
for more information.
BRAKE WARNING LAMP
The brake warning lamp warns the driver that the
parking brake is applied or that the pressures in the
two halves of the split brake hydraulic system are
unequal. With the ignition switch turned ON, battery
JINSTRUMENT PANEL AND GAUGESÐYJ 8E - 25