2002 JEEP GRAND CHEROKEE Instrument cluster electrical

²The speed signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
Once the speed control has been disengaged,
depressing the RES/ACCEL switch (when speed is
greater than 30 mph) restores the vehicle to the tar-
get speed that was stored in the PCM.
While the speed control is engaged, the driver can
increase the vehicle speed by depressing the RES/AC-
CEL switch. The new target speed is stored in the
PCM when the RES/ACCEL is released. The PCM
also has a9tap-up9feature in which vehicle speed
increases at a rate of approximately 2 mph for each
momentary switch activation of the RES/ACCEL
switch.
A ªtap downº feature is used to decelerate without
disengaging the speed control system. To decelerate
from an existing recorded target speed, momentarily
depress the COAST switch. For each switch activa-
tion, speed will be lowered approximately 1 mph.
OVERSHOOT/UNDERSHOOT
If the vehicle operator repeatedly presses and
releases the SET button with their foot off of the
accelerator (referred to as a ªlift foot setº), the vehicle
may accelerate and exceed the desired set speed by
up to 5 mph (8 km/h). It may also decelerate to less
than the desired set speed, before finally achieving
the desired set speed.
The Speed Control System has an adaptive strat-
egy that compensates for vehicle-to-vehicle variations
in speed control cable lengths. When the speed con-
trol is set with the vehicle operators foot off of the
accelerator pedal, the speed control thinks there is
excessive speed control cable slack and adapts
accordingly. If the ªlift foot setsº are continually used,
a speed control overshoot/undershoot condition will
develop.
To ªunlearnº the overshoot/undershoot condition,
the vehicle operator has to press and release the set
button while maintaining the desired set speed using
the accelerator pedal (not decelerating or accelerat-
ing), and then turning the cruise control switch to
the OFF position (or press the CANCEL button if
equipped) after waiting 10 seconds. This procedure
must be performed approximately 10±15 times to
completely unlearn the overshoot/undershoot condi-
tion.DIAGNOSIS AND TESTING - ROAD TEST
Perform a vehicle road test to verify reports of
speed control system malfunction. The road test
should include attention to the speedometer. Speed-
ometer operation should be smooth and without flut-
ter at all speeds.
Flutter in the speedometer indicates a problem
which might cause surging in the speed control sys-
tem. The cause of any speedometer problems should
be corrected before proceeding. Refer to Group 8J,
Instrument Cluster for speedometer diagnosis.
If a road test verifies a system problem and the
speedometer operates properly, check for:
²A Diagnostic Trouble Code (DTC). If a DTC
exists, conduct tests per the Powertrain Diagnostic
Procedures service manual.
²A misadjusted brake (stop) lamp switch. This
could also cause an intermittent problem.
²Loose, damaged or corroded electrical connec-
tions at the servo. Corrosion should be removed from
electrical terminals and a light coating of Mopar
MultiPurpose Grease, or equivalent, applied.
²Leaking vacuum reservoir.
²Loose or leaking vacuum hoses or connections.
²Defective one-way vacuum check valve.
²Secure attachment of both ends of the speed con-
trol servo cable.
²Smooth operation of throttle linkage and throttle
body air valve.
²Failed speed control servo. Do the servo vacuum
test.
CAUTION: When test probing for voltage or conti-
nuity at electrical connectors, care must be taken
not to damage connector, terminals or seals. If
these components are damaged, intermittent or
complete system failure may occur.
8P - 2 SPEED CONTROLWJ
SPEED CONTROL (Continued)

CONTROL/CENTRAL TIMER MODULE -
DESCRIPTION).
²Combination Flasher (Refer to 8 - ELECTRI-
CAL/LAMPS/LIGHTING - EXTERIOR/COMBINA-
TION FLASHER - DESCRIPTION).
²Door Ajar Switch (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - INTERIOR/DOOR AJAR
SWITCH - DESCRIPTION - DOOR AJAR SWITCH).
²Driver Cylinder Lock Switch (Refer to 8 - ELEC-
TRICAL/POWER LOCKS/DOOR CYLINDER LOCK/
UNLOCK SWITCH - DESCRIPTION).
²Hood Ajar Switch(Refer to 8 - ELECTRICAL/VE-
HICLE THEFT SECURITY/HOOD AJAR SWITCH -
DESCRIPTION).
²Horn Relay (Refer to 8 - ELECTRICAL/HORN/
HORN RELAY - DESCRIPTION).
²Liftgate Ajar Switch (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - INTERIOR/DOOR AJAR
SWITCH - DESCRIPTION - LIFTGATE AJAR
SWITCH).
²Liftgate Flip-Up Glass Ajar Switch(Refer to 8 -
ELECTRICAL/LAMPS/LIGHTING - INTERIOR/
DOOR AJAR SWITCH - DESCRIPTION - LIFTGATE
FLIP-UP GLASS AJAR SWITCH).
²Low Beam Headlamp Relay
²VTSS Indicator (Refer to 8 - ELECTRICAL/VE-
HICLE THEFT SECURITY/VTSS INDICATOR -
DESCRIPTION).
Certain functions and features of the VTSS rely
upon resources shared with or controlled by other
modules in the vehicle over the Programmable Com-
munications Interface (PCI) data bus network. The
other modules that may affect VTSS operation are:
²Driver Door Module (Refer to 8 - ELECTRICAL/
ELECTRONIC CONTROL MODULES/DOOR MOD-
ULE - DESCRIPTION).
²Passenger Door Module (Refer to 8 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/DOOR
MODULE - DESCRIPTION).
DESCRIPTION - SENTRY KEY IMMOBILIZER
SYSTEM
Vehicles equipped with the Sentry Key Immobilizer
System (SKIS) can be identified by the presence of
an amber SKIS indicator in the instrument cluster
that will illuminate for about three seconds each
time the ignition switch is turned to the On position,
or by a gray molded rubber cap on the head of the
ignition key. Models not equipped with SKIS still
have a SKIS indicator in the cluster, but it will not
illuminate. Also, models not equipped with the SKIS
have a black molded rubber cap on the head of the
ignition key.
The SKIS includes the following major components,
which are described in further detail elsewhere in
this service manual:²Powertrain Control Module
²Sentry Key Immobilizer Module
²Sentry Key Transponder
²SKIS Indicator
Except for the Sentry Key transponders, which rely
upon Radio Frequency (RF) communication, hard
wired circuitry connects the SKIS components to the
electrical system of the vehicle.Refer to the appropri-
ate wiring information.
OPERATION
OPERATION - VEHICLE THEFT SECURITY
SYSTEM
The Vehicle Theft Security System (VTSS) is
divided into two basic subsystems: Vehicle Theft
Alarm (VTA) and Sentry Key Immobilizer System
(SKIS). The following are paragraphs that briefly
describe the operation of each of those two sub-
systems.
A Body Control Module (BCM) is used to control
and integrate many of the functions and features
included in the Vehicle Theft Security System
(VTSS). In the VTSS, the BCM receives inputs indi-
cating the status of the door ajar switches, the driver
cylinder lock switch, the ignition switch, the liftgate
ajar switches, the liftgate flip-up glass ajar switch,
the power lock switches and, in vehicles so equipped,
the hood ajar switch. The programming in the BCM
allows it to process the information from all of these
inputs and send control outputs to energize or de-en-
ergize the combination flasher, the horn relay (except
vehicles with the premium version of the VTA), and
the VTSS indicator. In addition, in vehicles built for
certain markets where premium versions of the VTA
is required, the BCM also exchanges messages with
the Intrusion Transceiver Module (ITM) over the Pro-
grammable Communications Interface (PCI) data
buss network to provide the features found in this
version of the VTA. The control of these inputs and
outputs are what constitute all of the features of the
VTSS. Following is information on the operation of
each of the VTSS features.
ENABLING
The BCM must have the VTSS function enabled in
order for the VTSS to perform as designed. The logic
in the BCM keeps its VTSS function dormant until it
is enabled using a DRBIIItscan tool. Refer to the
appropriate diagnostic information.
PRE-ARMING
The VTA has a pre-arming sequence. Pre-arming
occurs when a door, the tailgate, or the flip-up glass
is open when the vehicle is locked using a power lock
8Q - 2 VEHICLE THEFT SECURITYWJ
VEHICLE THEFT SECURITY (Continued)

DIAGNOSIS AND TESTING - SENTRY KEY
IMMOBILIZER SYSTEM
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
SENTRY KEY IMMOBILIZER SYSTEM DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
SKIS INDICATOR FAILS TO
LIGHT DURING BULB TEST1. Bulb faulty. 1. Perform the instrument cluster actuator test.
(Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING -
ACTUATOR TEST). Replace the faulty bulb, if
required.
2. Fuse faulty. 2. Check the SKIM fused B(+) fuse and the fused
ignition switch output (st-run) fuse in the JB.
Replace fuses, if required.
3. Ground path faulty. 3. Check for continuity to ground at the connector
for the SKIM. Repair wiring, if required.
4. Battery feed faulty. 4. Check for battery current at the connector for
the SKIM. Repair wiring, if required.
5. Ignition feed faulty. 5. Check for battery current at the connector for
the SKIM with the ignition switch in the On
position. Repair wiring, if required.
SKIS INDICATOR FLASHES
FOLLOWING BULB TEST1. Invalid key in ignition
switch lock cylinder.1. Replace the key with a known valid key.
2. Key-related fault. 2. Use a DRBIIITscan tool and the appropriate
diagnostic information for further diagnosis.
SKIS INDICATOR LIGHTS
SOLID FOLLOWING BULB
TEST1. SKIS system malfunction/
fault detected.1. Use a DRBIIITscan tool and the appropriate
diagnostic information for further diagnosis.
2. SKIS system inoperative. 2. Use a DRBIIITscan tool and the appropriate
diagnostic information for further diagnosis.
SKIS INDICATOR FAILS TO LIGHT DURING BULB TEST
If the Sentry Key Immobilizer System (SKIS) indi-
cator in the instrument cluster fails to illuminate for
about three seconds after the ignition switch is
turned to the On position (bulb test), perform the
instrument cluster actuator test. (Refer to 8 - ELEC-
TRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING - ACTUATOR TEST). If the bulb
fails to operate during the actuator test, replace the
bulb. If the SKIS indicator still fails to light during
the bulb test, a wiring problem resulting in the loss
of battery current or ground to the Sentry Key Immo-
bilizer Module (SKIM) should be suspected, and thefollowing procedure should be used for diagnosis.
Refer to the appropriate wiring information.
NOTE: The following tests may not prove conclu-
sive in the diagnosis of this system. The most reli-
able, efficient, and accurate means to diagnose the
Sentry Key Immobilizer System requires the use of
a DRBIIITscan tool. Refer to the appropriate diag-
nostic information.
(1) Check the fused B(+) fuse in the Junction
Block (JB). If OK, go to Step 2. If not OK, repair the
shorted circuit or component and replace the faulty
fuse.
WJVEHICLE THEFT SECURITY 8Q - 5
VEHICLE THEFT SECURITY (Continued)

(2) Check for battery voltage at the fused B(+) fuse
in the JB. If OK, go to Step 3. If not OK, repair the
open B(+) circuit between the JB fuse and the Power
Distribution Center (PDC).
(3) Check the fused ignition switch output (st-run)
fuse in the JB. If OK, go to Step 4. If not OK, repair
the shorted circuit or component and replace the
faulty fuse.
(4) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (st-run) fuse in the JB. If OK, go to Step 5. If
not OK, repair the open fused ignition switch output
(st-run) circuit between the JB fuse and the ignition
switch as required.
(5) Disconnect and isolate the battery negative
cable. Disconnect the instrument panel wire harness
connector for the Sentry Key Immobilizer Module
(SKIM) from the SKIM connector. Check for continu-
ity between the ground circuit of the instrument
panel wire harness connector for the SKIM and a
good ground. There should be continuity. If OK, go to
Step 6. If not OK, repair the open ground circuit.
(6) Reconnect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
instrument panel wire harness connector for the
SKIM. If OK, go to Step 7. If not OK, repair the open
fused B(+) circuit between the SKIM and the JB
fuse.
(7) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (st-run) circuit of the instrument panel wire
harness connector for the SKIM. If OK, refer to the
appropriate diagnostic information and use a
DRBIIItscan tool to complete the diagnosis of the
SKIS. If not OK, repair the open fused ignition
switch output (st-run) circuit between the SKIM and
the JB fuse.
SKIS INDICATOR FLASHES OR LIGHTS SOLID FOLLOWING
BULB TEST
A SKIS indicator that flashes following a successful
bulb test indicates that an invalid key has been
detected, or that a key-related fault has been set. A
SKIS indicator that lights solid following a successful
bulb test indicates that the SKIM has detected a sys-
tem malfunction or that the SKIS is inoperative. In
either case, fault information will be stored in the
SKIM memory. For retrieval of this fault information
and further diagnosis of the SKIS, the PCI data bus,
the SKIM message outputs to the instrument cluster,
the SKIM message outputs to the Body Control Mod-
ule (BCM), or the message inputs and outputs
between the SKIM and the Powertrain Control Mod-
ule (PCM), a DRBIIItscan tool and the appropriate
diagnostic information are required. Following are
preliminary troubleshooting guidelines to be followed
during diagnosis using a DRBIIItscan tool:(1) Using the DRBIIItscan tool, read and record
the faults as they exist in the SKIM when you first
begin your diagnosis of the vehicle. It is important to
document these faults because the SKIM does not
differentiate between historical and active faults. If
this problem turns out to be an intermittent condi-
tion, this information may become invaluable to your
diagnosis.
(2) Using the DRBIIItscan tool, erase all of the
faults from the SKIM.
(3) Cycle the ignition switch to the Off position,
then back to the On position.
(4) Using the DRBIIItscan tool, read any faults
that are now present in the SKIM. These are the
active faults.
(5) Using this active fault information, refer to the
proper procedure in the appropriate diagnostic infor-
mation for the additional specific diagnostic steps.
STANDARD PROCEDURE
STANDARD PROCEDURE - SKIS
INITIALIZATION
The Sentry Key Immobilizer System (SKIS) must
be initialized following a Sentry Key Immobilizer
Module (SKIM) replacement. SKIS initialization
requires the use of a DRBIIItscan tool. Initialization
will also require that you have access to the unique
four-digit PIN code that was assigned to the original
SKIM. The PIN codemustbe used to enter the
Secured Access Mode in the SKIM. This PIN number
may be obtained from the vehicle owner, from the
original vehicle invoice, or from the DaimlerChrysler
Customer Center. (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES - STANDARD PRO-
CEDURE - PCM/SKIM PROGRAMMING).
NOTE: If a Powertrain Control Module (PCM) is
replaced on a vehicle equipped with the Sentry Key
Immobilizer System (SKIS), the unique Secret Key
data must be transferred from the Sentry Key
Immobilizer Module (SKIM) to the new PCM using
the PCM replacement procedure. This procedure
also requires the use of a DRBIIITscan tool and the
unique four-digit PIN code to enter the Secured
Access Mode in the SKIM. Refer to the appropriate
diagnostic information for the proper PCM replace-
ment procedures.
STANDARD PROCEDURE - SENTRY KEY
TRANSPONDER PROGRAMMING
All Sentry Keys included with the vehicle are pre-
programmed to work with the Sentry Key Immobi-
lizer System (SKIS) when it is shipped from the
8Q - 6 VEHICLE THEFT SECURITYWJ
VEHICLE THEFT SECURITY (Continued)

message inputs to and outputs from the alarm siren
module requires the use of a DRBIIItscan tool.
Refer to the appropriate diagnostic information.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Disconnect the alarm siren module wiring har-
ness connector. (Fig. 9).
(3) Remove the screws that secure the alarm siren
module to the left frame rail.
(4) Remove the alarm siren module.
INSTALLATION
(1) Position the alarm siren module on to the left
frame rail. (Fig. 9).
(2) Install and tighten the screws that secure the
alarm siren moduleto the frame rail. Tighten the
screws to 6 N´m (50 in. lbs.).
(3) Reconnect the alarm siren module wiring har-
ness connector.
(4) Reconnect the battery negative cable.
NOTE: If the alarm siren module has been replaced
with a new unit, the new unit MUST be configured
in the Intrusion Transceiver Module (ITM) before the
Vehicle Theft Security System can operate as
designed. The use of a DRBIIITscan tool is requiredto configure the alarm siren module settings in the
ITM. Refer to the appropriate diagnostic informa-
tion.
SKIS INDICATOR LAMP
DESCRIPTION
A Sentry Key Immobilizer System (SKIS) indicator
lamp is standard equipment on all instrument clus-
ters, but is only functional on vehicles equipped with
the optional SKIS. The amber SKIS indicator lamp is
located to the right of the oil pressure gauge.
OPERATION
The Sentry Key Immobilizer System (SKIS) indica-
tor lamp gives an indication to the vehicle operator of
the status of the SKIS. This lamp is controlled by a
transistor on the instrument cluster circuit board
based upon messages received by the cluster from
the Sentry Key Immobilizer Module (SKIM) over the
Programmable Communications Interface (PCI) data
bus. The SKIS indicator lamp bulb receives battery
current on the instrument cluster circuit board
through the fused ignition switch output (st-run) cir-
cuit whenever the ignition switch is in the On or
Start positions. The lamp bulb only illuminates when
it is provided a path to ground by the instrument
cluster transistor. The instrument cluster will turn
on the SKIS indicator lamp for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position, the SKIM tells the cluster
to illuminate the lamp for about three seconds.
²SKIS Lamp-On Message- Each time the clus-
ter receives a SKIS lamp-on message from the SKIM,
the lamp will be illuminated. The lamp can be
flashed on and off, or illuminated solid, as dictated
by the message from the SKIM. For more informa-
tion on the SKIS and the SKIS lamp control param-
eters, (Refer to 8 - ELECTRICAL/VEHICLE THEFT
SECURITY - OPERATION - SENTRY KEY IMMO-
BILIZER SYSTEM). The lamp remains illuminated
until the cluster receives a lamp-off message from
the SKIM or until the ignition switch is turned to the
Off position, whichever occurs first.
²Actuator Test- Each time the cluster is put
through the actuator test, the lamp will be turned on
for the duration of the test to confirm the functional-
ity of the lamp and the cluster.
The SKIM performs a self-test each time the igni-
tion switch is turned to the On position to decide
whether the system is in good operating condition.
The SKIM then sends a message to the instrument
cluster. If the SKIS indicator lamp fails to light dur-
ing the bulb test, replace the bulb. For further diag-
nosis of the SKIS indicator lamp or the instrument
Fig. 9 Siren Remove/Install
1 - SIREN
2 - FRAME
8Q - 14 VEHICLE THEFT SECURITYWJ
SIREN (Continued)

cluster circuitry that controls the lamp, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNO-
SIS AND TESTING). If the instrument cluster turns
on the SKIS indicator lamp after the bulb test, either
solid or flashing, it indicates that a SKIS malfunction
has occurred or that the SKIS is inoperative. For
proper diagnosis of the SKIS, the PCI data bus, or
the message inputs to the instrument cluster that
control the SKIS indicator lamp, a DRBIIItscan tool
and the appropriate diagnostic information are
required.
TRANSPONDER KEY
DESCRIPTION
Each ignition key used in the Sentry Key Immobi-
lizer System (SKIS) has an integral transponder chip
(Fig. 10). Ignition keys with this feature can be
readily identified by a gray rubber cap molded onto
the head of the key, while conventional ignition keys
have a black molded rubber cap. The transponder
chip is concealed beneath the molded rubber cap,
where it is molded into the head of the metal key.
Each new Sentry Key has a unique transponder iden-
tification code permanently programmed into it by
the manufacturer. The Sentry Key transponder if
faulty or damaged, must be replaced.
OPERATION
When the ignition switch is turned to the On posi-
tion, the Sentry Key Immobilizer Module (SKIM)communicates through its antenna with the Sentry
Key transponder using a Radio Frequency (RF) sig-
nal. The SKIM then waits for a RF response from the
transponder through the same antenna. The Sentry
Key transponder chip is within the range of the
SKIM transceiver antenna ring when it is inserted
into the ignition lock cylinder. The SKIM determines
whether a valid key is present in the ignition lock
cylinder based upon the response from the transpon-
der. If a valid key is detected, that fact is communi-
cated by the SKIM to the Powertrain Control Module
(PCM) over the Programmable Communications
Interface (PCI) data bus, and the PCM allows the
engine to continue running. If the PCM receives an
invalid key message, or receives no message from the
SKIM over the PCI data bus, the engine will be dis-
abled after about two seconds of operation. The Elec-
troMechanical Instrument Cluster (EMIC) will also
respond to the invalid key message on the PCI data
bus by flashing the SKIS indicator on and off.
Each Sentry Key has a unique transponder identi-
fication code permanently programmed into it by the
manufacturer. Likewise, the SKIM has a unique
Secret Key code programmed into it by the manufac-
turer. When a Sentry Key is programmed into the
memory of the SKIM, the SKIM stores the transpon-
der identification code from the Sentry Key, and the
Sentry Key learns the Secret Key code from the
SKIM. Once the Sentry Key learns the Secret Key
code of the SKIM, it is permanently stored in the
memory of the transponder. Therefore, once a Sentry
Key has been programmed to a particular vehicle, it
cannot be used on any other vehicle. (Refer to 8 -
ELECTRICAL/VEHICLE THEFT SECURITY -
STANDARD PROCEDURE - TRANSPONDER PRO-
GRAMMING).
VTSS INDICATOR
DESCRIPTION
The Vehicle Theft Security System (VTSS) indica-
tor consists of a red Light-Emitting Diode that is
mounted and integral to the automatic headlamp
light sensor photo diode unit, which is located on the
top of the instrument panel. The remainder of the
housing including the mount and the electrical con-
nection are concealed beneath the instrument panel
top cover.
The VTSS indicator cannot be adjusted or repaired
the entire automatic headlamp light sensor/VTSS
indicator must be replaced. (Refer to 8 - ELECTRI-
CAL/LAMPS/LIGHTING - EXTERIOR/AUTO HEAD-
LAMP SENSOR - REMOVAL).
Fig. 10 Sentry Key Immobilizer Transponder
1 - MOLDED CAP
2 - TRANSPONDER CHIP
3 - MOLDED CAP REMOVED
4 - TRANSPONDER KEY
WJVEHICLE THEFT SECURITY 8Q - 15
SKIS INDICATOR LAMP (Continued)

(3) Apply a small amount of clean engine oil to
o-rings.
(4) Position filter/regulator to body and install 2
bolts. Tighten bolts to 3 N´m (30 in. lbs.) torque.
(5) Connect 3 fittings. Refer to Quick-Connect Fit-
tings.
(6) Connect negative battery cable to battery.
(7) Start engine and check for leaks.
FUEL LEVEL SENDING UNIT /
SENSOR
DESCRIPTION
The fuel gauge sending unit (fuel level sensor) is
attached to the side of the fuel pump module. The
sending unit consists of a float, an arm, and a vari-
able resistor track (card).
OPERATION
The fuel pump module has 4 different circuits
(wires). Two of these circuits are used for the fuel
gauge sending unit for fuel gauge operation, and for
certain OBD II emission requirements. The other 2
wires are used for electric fuel pump operation.
For Fuel Gauge Operation:A constant input
voltage source of about 12 volts (battery voltage) is
supplied to the resistor track on the fuel gauge send-
ing unit. This is fed directly from the Powertrain
Control Module (PCM).NOTE: For diagnostic pur-
poses, this 12V power source can only be veri-fied with the circuit opened (fuel pump module
electrical connector unplugged). With the con-
nectors plugged, output voltages will vary from
about 0.6 volts at FULL, to about 8.6 volts at
EMPTY (about 8.6 volts at EMPTY for Jeep
models, and about 7.0 volts at EMPTY for
Dodge Truck models).The resistor track is used to
vary the voltage (resistance) depending on fuel tank
float level. As fuel level increases, the float and arm
move up, which decreases voltage. As fuel level
decreases, the float and arm move down, which
increases voltage. The varied voltage signal is
returned back to the PCM through the sensor return
circuit.
Both of the electrical circuits between the fuel
gauge sending unit and the PCM are hard-wired (not
multi-plexed). After the voltage signal is sent from
the resistor track, and back to the PCM, the PCM
will interpret the resistance (voltage) data and send
a message across the multi-plex bus circuits to the
instrument panel cluster. Here it is translated into
the appropriate fuel gauge level reading. Refer to
Instrument Panel for additional information.
For OBD II Emission Monitor Requirements:
The PCM will monitor the voltage output sent from
the resistor track on the sending unit to indicate fuel
level. The purpose of this feature is to prevent the
OBD II system from recording/setting false misfire
and fuel system monitor diagnostic trouble codes.
The feature is activated if the fuel level in the tank
is less than approximately 15 percent of its rated
capacity. If equipped with a Leak Detection Pump
(EVAP system monitor), this feature will also be acti-
vated if the fuel level in the tank is more than
approximately 85 percent of its rated capacity.
DIAGNOSIS AND TESTING - FUEL LEVEL
SENDING UNIT
The fuel level sending unit contains a variable
resistor (track). As the float moves up or down, elec-
trical resistance will change. Refer to Instrument
Panel and Gauges for Fuel Gauge testing. To test the
gauge sending unit only, it must be removed from
vehicle. The unit is part of the fuel pump module.
Refer to Fuel Pump Module Removal/Installation for
procedures. Measure the resistance across the send-
ing unit terminals. With float in up position, resis-
tance should be 20 ohms (+/- 5%). With float in down
position, resistance should be 270 ohms (+/- 5%).
REMOVAL
The fuel gauge sending unit (fuel level sensor) and
float assembly is located on the side of fuel pump
module (Fig. 6). The fuel pump module is located
within the fuel tank.
Fig. 5 Fuel Filter/Fuel Pressure Regulator Removal/
Installation
1 - FUEL FILTER/FUEL PRESSURE REGULATOR
2 - MOUNTING BOLTS (2)
WJFUEL DELIVERY 14 - 7
FUEL FILTER/PRESSURE REGULATOR (Continued)

REMOVAL
WARNING: BEFORE SERVICING THE STEERING
COLUMN THE AIRBAG SYSTEM MUST BE DIS-
ARMED. FAILURE TO DO SO MAY RESULT IN ACCI-
DENTAL DEPLOYMENT OF THE AIRBAG AND
POSSIBLE PERSONAL INJURY.(Refer to 8 - ELEC-
TRICAL/RESTRAINTS/DRIVER AIRBAG - REMOVAL).
(1) Position front wheels straight ahead.
(2) Disconnect and isolate the negative (ground)
cable from the battery.
(3) Remove the airbag,(Refer to 8 - ELECTRICAL/
RESTRAINTS/DRIVER AIRBAG - REMOVAL).
(4) Remove the steering wheel nut and remove
wheel with Puller C-3894-A (Fig. 2).
NOTE: Ensure the puller jaws are seated in the
pockets (Fig. 3) of the steering wheel armature.(5) Remove the cluster bezel by pulling it from the
instrument panel (Fig. 4).
Fig. 2 Steering Wheel Puller
1 - PULLER
2 - STEERING WHEEL
Fig. 3 Steering Wheel Pockets
1 - STEERING WHEEL POCKETS
Fig. 4 Cluster Bezel
1 - CLUSTER
2 - CLUSTER BEZEL
3 - STEERING COLUMN
4 - KNEE BLOCKER COVER
19 - 8 COLUMNWJ
COLUMN (Continued)