2002 JEEP LIBERTY Ground main

(4) Connect the ohmmeter between terminals 87
and 30. The ohmmeter should not show continuity at
this time.
(5) Connect one end of a jumper wire (16 gauge or
smaller) to relay terminal 85. Connect the other end
of the jumper wire to the ground side of a 12 volt
power source.
(6) Connect one end of another jumper wire (16
gauge or smaller) to the power side of the 12 volt
power source.Do not attach the other end of the
jumper wire to the relay at this time.
WARNING: DO NOT ALLOW OHMMETER TO CON-
TACT TERMINALS 85 OR 86 DURING THIS TEST.
DAMAGE TO OHMMETER MAY RESULT.
(7) Attach the other end of the jumper wire to
relay terminal 86. This activates the relay. The ohm-
meter should now show continuity between relay ter-
minals 87 and 30. The ohmmeter should not show
continuity between relay terminals 87A and 30.
(8) Disconnect jumper wires.
(9) Replace the relay if it did not pass the continu-
ity and resistance tests. If the relay passed the tests,
it operates properly. Check the remainder of the ASD
and fuel pump relay circuits. Refer to 8, Wiring Dia-
grams.
REMOVAL
The ASD relay is located in the Power Distribution
Center (PDC) (Fig. 4). Refer to label on PDC cover
for relay location.(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
The ASD relay is located in the Power Distribution
Center (PDC). Refer to label on PDC cover for relay
location.
(1) Install relay to PDC.
(2) Install cover to PDC.
CAMSHAFT POSITION
SENSOR
DESCRIPTION
DESCRIPTION - 2.4L
The Camshaft Position Sensor (CMP) on the 2.4L
4±cylinder engine is bolted to the right-front side of
the cylinder head (Fig. 5).
Fig. 4 POWER DISTRIBUTION CENTER (PDC)
1 - BATTERY
2 - PDC
3 - PDC COVER
Fig. 5 CMP LOCATION - 2.4L
1 - CMP SENSOR
2 - ELECTRICAL CONNECTOR
3-
4 - SLOTTED HOLES
5 - MOUNTING BOLTS (2)
KJIGNITION CONTROL 8I - 5
AUTO SHUT DOWN RELAY (Continued)

REMOVAL
2.4L
If spark plug for #2 or #3 cylinder is being
removed, throttle body must be removed. Refer to
Throttle Body Removal.
(1) Remove air cleaner tube and housing.
(2) Twist secondary cable at cylinder head to break
loose at spark plug. Remove cable from plug.
(3) Prior to removing spark plug, spray com-
pressed air into cylinder head opening. This will help
prevent foreign material from entering combustion
chamber.
(4) Remove spark plug from cylinder head using a
quality socket with a rubber or foam insert.
(5) Inspect spark plug condition. Refer to Spark
Plug Conditions.
3.7L
Each individual spark plug is located under each
ignition coil. Each individual ignition coil must be
removed to gain access to each spark plug. Refer to
Ignition Coil Removal/Installation.
(1) Prior to removing ignition coil, spray com-
pressed air around coil base at cylinder head.
(2) Prior to removing spark plug, spray com-
pressed air into cylinder head opening. This will help
prevent foreign material from entering combustion
chamber.
(3) Remove spark plug from cylinder head using a
quality socket with a rubber or foam insert. Also
check condition of ignition coil o-ring and replace as
necessary.
(4) Inspect spark plug condition. Refer to Spark
Plug Conditions.
CLEANING SPARK PLUGS
The plugs may be cleaned using commercially
available spark plug cleaning equipment. After clean-
ing, file the center electrode flat with a small point
file or jewelers file before adjusting gap.
CAUTION: Never use a motorized wire wheel brush
to clean the spark plugs. Metallic deposits will
remain on the spark plug insulator and will cause
plug misfire.
INSTALLATION
2.4L
CAUTION: Spark plug tightening on the 2.4L is
torque critical. The plugs are equipped with tapered
seats. Do not exceed 15 ft. lbs. torque.
Special care should be taken when installing spark
plugs into the cylinder head spark plug wells. Be
sure the plugs do not drop into the plug wells as elec-
trodes can be damaged.
Always tighten spark plugs to the specified torque.
Over tightening can cause distortion resulting in a
change in the spark plug gap or a cracked porcelain
insulator.
(1) Start the spark plug into the cylinder head by
hand to avoid cross threading.
(2) Tighten spark plugs. Refer to torque specifica-
tions.
(3) Install throttle body. Refer to Throttle Body
Installation.
(4) Install air cleaner tube and housing.
3.7L
Special care should be taken when installing spark
plugs into the cylinder head spark plug wells. Be
Fig. 26 Preignition Damage
1 - GROUND ELECTRODE STARTING TO DISSOLVE
2 - CENTER ELECTRODE DISSOLVED
Fig. 27 Spark Plug Overheating
1 - BLISTERED WHITE OR GRAY COLORED INSULATOR
KJIGNITION CONTROL 8I - 15
SPARK PLUG (Continued)

gauge readings during normal operation that are con-
sistent with customer expectations. However, when
abnormal conditions exist such as high coolant tem-
perature, the algorithm can drive the gauge pointer
to an extreme position and the microprocessor can
sound a chime through the on-board chime tone gen-
erator to provide distinct visual and audible indica-
tions of a problem to the vehicle operator. The
instrument cluster circuitry may also perform chime
service for other electronic modules in the vehicle
based upon electronic chime tone request messages
received over the PCI data bus to provide the vehicle
operator with an audible alert to supplement a visual
indication. One such alert is a door ajar warning
chime, which the EMIC provides by monitoring PCI
bus messages from the Body Control Module (BCM).
The EMIC circuitry operates on battery current
received through a fused B(+) fuse in the Junction
Block (JB) on a non-switched fused B(+) circuit, and
on battery current received through a fused ignition
switch output (run-start) fuse in the JB on a fused
ignition switch output (run-start) circuit. This
arrangement allows the EMIC to provide some fea-
tures regardless of the ignition switch position, while
other features will operate only with the ignition
switch in the On or Start positions. The EMIC
receives a ground input from the BCM as a wake-up
signal in order to provide the ignition-off features.
The EMIC circuitry is grounded through a ground
circuit and take out of the instrument panel wire
harness with an eyelet terminal connector that is
secured by a nut to a ground stud located on the left
instrument panel end bracket.
The EMIC also has a self-diagnostic actuator test
capability, which will test each of the PCI bus mes-
sage-controlled functions of the cluster by lighting
the appropriate indicators (except the airbag indica-
tor), sweeping the gauge needles to several calibra-
tion points across the gauge faces, and stepping the
odometer display sequentially from all ones through
all nines. (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). See the
owner's manual in the vehicle glove box for more
information on the features, use and operation of the
EMIC.
GAUGES All gauges receive battery current
through the EMIC circuitry when the ignition switch
is in the On or Start positions. With the ignition
switch in the Off position battery current is not sup-
plied to any gauges, and the EMIC circuitry is pro-
grammed to move all of the gauge needles back to
the low end of their respective scales. Therefore, the
gauges do not accurately indicate any vehicle condi-
tion unless the ignition switch is in the On or Start
positions. All of the EMIC gauges, except the odome-
ter, are air core magnetic units. Two fixed electro-magnetic coils are located within each gauge. These
coils are wrapped at right angles to each other
around a movable permanent magnet. The movable
magnet is suspended within the coils on one end of a
pivot shaft, while the gauge needle is attached to the
other end of the shaft. One of the coils has a fixed
current flowing through it to maintain a constant
magnetic field strength. Current flow through the
second coil changes, which causes changes in its
magnetic field strength. The current flowing through
the second coil is changed by the EMIC circuitry in
response to messages received over the PCI data bus.
The gauge needle moves as the movable permanent
magnet aligns itself to the changing magnetic fields
created around it by the electromagnets.
The gauges are diagnosed using the EMIC self-di-
agnostic actuator test. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). Proper testing of the PCI data bus and
the electronic data bus message inputs to the EMIC
that control each gauge require the use of a DRBIIIt
scan tool. Refer to the appropriate diagnostic infor-
mation. Specific operation details for each gauge may
be found elsewhere in this service information.
VACUUM-FLUORESCENT DISPLAY The Vacu-
um-Fluorescent Display (VFD) module is soldered to
the EMIC circuit board. The display is active when
the driver door is opened with the ignition switch in
the Off or Accessory positions (Rental Car mode), and
with the ignition switch in the On or Start positions.
The VFD is inactive when the ignition switch is in
the Off or Accessory positions and the driver door is
closed. The illumination intensity of the VFD is con-
trolled by the EMIC circuitry based upon electronic
dimming level messages received from the BCM over
the PCI data bus, and is synchronized with the illu-
mination intensity of other VFDs in the vehicle. The
BCM provides dimming level messages based upon
internal programming and inputs it receives from the
control knob and control ring on the left (lighting)
control stalk of the multi-function switch on the
steering column.
The VFD has several display capabilities including
odometer, trip odometer, and warning messages
whenever the appropriate conditions exist. The VFD
warning messages include:
²ªdoorº- indicating a door is ajar.
²ªgateº- indicating the tailgate is ajar.
²ªglassº- indicating the tailgate glass is ajar.
²ªlowashº- indicating that the washer fluid
level is low.
²ªno busº- indicating there is no PCI data bus
communication detected.
An odometer/trip odometer switch on the EMIC cir-
cuit board is used to control the display modes. This
switch is actuated manually by depressing the odom-
KJINSTRUMENT CLUSTER 8J - 5
INSTRUMENT CLUSTER (Continued)

eter/trip odometer switch button that extends
through the lower edge of the cluster lens, just right
of the speedometer. Actuating this switch momen-
tarily with the ignition switch in the On position will
toggle the VFD between the odometer and trip odom-
eter modes. Depressing the switch button for about
two seconds while the VFD is in the trip odometer
mode will reset the trip odometer value to zero. Hold-
ing this switch depressed while turning the ignition
switch from the Off position to the On position will
initiate the EMIC self-diagnostic actuator test. The
VFD will also display the cluster software version
level near the completion of the EMIC self-diagnostic
actuator test. Refer to the appropriate diagnostic
information for additional details on this VFD func-
tion.
The VFD is diagnosed using the EMIC self-diag-
nostic actuator test. (Refer to 8 - ELECTRICAL/IN-
STRUMENT CLUSTER - DIAGNOSIS AND
TESTING). Proper testing of the PCI data bus and
the electronic data bus message inputs to the EMIC
that control some of the VFD functions requires the
use of a DRBIIItscan tool. Refer to the appropriate
diagnostic information. Specific operation details for
the odometer, the trip odometer, and the various
warning message functions of the VFD may be found
elsewhere in this service information.
INDICATORS Indicators are located in various
positions within the EMIC and are all connected to
the EMIC circuit board. The turn signal indicators,
security indicator, washer fluid indicator, and coolant
low indicator (diesel engine only) use hard wired
inputs to the EMIC. The brake indicator is controlled
by PCI data bus messages from the Controller
Antilock Brake (CAB) as well as by hard wired park
brake switch and brake fluid level switch inputs to
the EMIC. The Malfunction Indicator Lamp (MIL) is
normally controlled by PCI data bus messages from
the Powertrain Control Module (PCM); however, if
the EMIC loses PCI data bus communication, the
EMIC circuitry will automatically turn the MIL on
until PCI data bus communication is restored. The
EMIC uses PCI data bus messages from the Body
Control Module (BCM), the PCM, the Airbag Control
Module (ACM), and the CAB to control all of the
remaining indicators.
The various indicators are controlled by different
strategies; some receive fused ignition switch output
from the EMIC circuitry and have a switched ground,
others are grounded through the EMIC circuitry and
have a switched battery feed, while still others are
completely controlled by the EMIC microprocessor
based upon various hard wired and electronic mes-
sage inputs. Some indicators are illuminated at a
fixed intensity, while the illumination intensity ofothers is synchronized with that of the EMIC general
illumination lamps.
In addition, certain indicators in this instrument
cluster are automatically configured or self-config-
ured. This feature allows the configurable indicators
to be enabled by the EMIC circuitry for compatibility
with certain optional equipment. The ABS indicator,
airbag indicator, SKIS indicator are automatically
configured by PCI data bus messages received by the
EMIC from the CAB, ACM, or Sentry Key Immobi-
lizer Module (SKIM) after the EMIC is installed in
the vehicle. Once these configuration settings are
learned by the EMIC, the DRBIIItscan tool must be
used to remove these settings from the EMIC non-
volatile memory. The self-configured indicators
remain latent in each EMIC at all times and will be
activated only when the EMIC receives the appropri-
ate PCI message inputs for the optional system or
equipment.
The hard wired indicators are diagnosed using con-
ventional diagnostic methods. The EMIC and PCI
bus message controlled indicators are diagnosed
using the EMIC self-diagnostic actuator test. (Refer
to 8 - ELECTRICAL/INSTRUMENT CLUSTER -
DIAGNOSIS AND TESTING). Proper testing of the
PCI data bus and the electronic data bus message
inputs to the EMIC that control each indicator
require the use of a DRBIIItscan tool. Refer to the
appropriate diagnostic information. Specific details of
the operation for each indicator may be found else-
where in this service information.
CLUSTER ILLUMINATION The EMIC has several
illumination lamps that are illuminated when the
exterior lighting is turned on with the headlamp
(multi-function) switch. The illumination intensity of
these lamps is adjusted by a 12-volt Pulse Width
Modulated (PWM) output of the EMIC when the
interior lighting control ring on the left control stalk
of the multi-function switch is rotated (down to dim,
up to brighten) to one of six available minor detent
positions. The BCM provides electronic dimming
level messages based upon internal programming
and inputs it receives from the control knob and con-
trol ring on the left (lighting) control stalk of the
multi-function switch on the steering column, then
provides a control output to energize or de-energize
the park lamp relay as appropriate. The energized
park lamp relay provides battery current to the
EMIC on the hard wired fused park lamp relay out-
put circuit, and the BCM provides the electronic dim-
ming level message to the EMIC over the PCI data
bus. The EMIC electronic circuitry provides the
proper PWM output to the cluster illumination lamps
and the VFD on the EMIC circuit board, then pro-
vides a synchronized PWM output on the hard wired
8J - 6 INSTRUMENT CLUSTERKJ
INSTRUMENT CLUSTER (Continued)

illuminates when it is provided a path to ground by
the instrument cluster transistor. The instrument
cluster will turn on the ABS indicator for the follow-
ing reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the ABS indicator is illu-
minated by the cluster for about three seconds as a
bulb test.
²ABS Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the CAB, the
ABS indicator will be illuminated. The indicator
remains illuminated until the cluster receives a
lamp-off message from the CAB, or until the ignition
switch is turned to the Off position, whichever occurs
first.
²Communication Error- If the cluster receives
no lamp-on or lamp-off messages from the CAB for
six consecutive seconds, the ABS indicator is illumi-
nated. The indicator remains illuminated until the
cluster receives a valid message from the CAB, or
until the ignition switch is turned to the Off position,
whichever occurs first.
²Actuator Test- Each time the instrument clus-
ter is put through the actuator test, the ABS indica-
tor will be turned on, then off again during the bulb
check portion of the test to confirm the functionality
of the LED and the cluster control circuitry.
²ABS Diagnostic Test- The ABS indicator is
blinked on and off by lamp-on and lamp-off messages
from the CAB during the performance of the ABS
diagnostic tests.
The CAB continually monitors the ABS circuits
and sensors to decide whether the system is in good
operating condition. The CAB then sends the proper
lamp-on or lamp-off messages to the instrument clus-
ter. If the CAB sends a lamp-on message after the
bulb test, it indicates that the CAB has detected a
system malfunction and/or that the ABS system has
become inoperative. The CAB will each store a Diag-
nostic Trouble Code (DTC) for any malfunction it
detects. Each time the ABS indicator fails to light
due to an open or short in the cluster ABS indicator
circuit, the cluster sends a message notifying the
CAB of the condition, then the instrument cluster
and the CAB will each store a DTC. For proper diag-
nosis of the antilock brake system, the CAB, the PCI
data bus, or the message inputs to the instrument
cluster that control the ABS indicator, a DRBIIIt
scan tool is required. Refer to the appropriate diag-
nostic information.AIRBAG INDICATOR
DESCRIPTION
An airbag indicator is standard equipment on all
instrument clusters. However, the instrument cluster
is programmed to automatically enable this indicator
only on vehicles equipped with the airbag system,
which is not available in some markets. The airbag
indicator is located above the fuel gauge and to the
left of the tachometer in the instrument cluster. The
airbag indicator consists of a stencil-like cutout of the
words ªAIR BAGº in the opaque layer of the instru-
ment cluster overlay. The dark outer layer of the
overlay prevents the indicator from being clearly vis-
ible when it is not illuminated. A red Light Emitting
Diode (LED) behind the cutout in the opaque layer of
the overlay causes the ªAIR BAGº text to appear in
red through the translucent outer layer of the over-
lay when it is illuminated from behind by the LED,
which is soldered onto the instrument cluster elec-
tronic circuit board. The airbag indicator is serviced
as a unit with the instrument cluster.
OPERATION
The airbag indicator gives an indication to the
vehicle operator when the airbag system is faulty or
inoperative. The airbag indicator is controlled by a
transistor on the instrument cluster circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the Airbag Control
Module (ACM) over the Programmable Communica-
tions Interface (PCI) data bus. The airbag indicator
Light Emitting Diode (LED) is completely controlled
by the instrument cluster logic circuit, and that logic
will only allow this indicator to operate when the
instrument cluster receives a battery current input
on the fused ignition switch output (run-start) cir-
cuit. Therefore, the LED will always be off when the
ignition switch is in any position except On or Start.
The LED only illuminates when it is provided a path
to ground by the instrument cluster transistor. The
instrument cluster will turn on the airbag indicator
for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the airbag indicator is illu-
minated for about six seconds. The entire six second
bulb test is a function of the ACM.
²ACM Lamp-On Message- Each time the clus-
ter receives a lamp-on message from the ACM, the
airbag indicator will be illuminated. The indicator
remains illuminated for about twelve seconds or until
the cluster receives a lamp-off message from the
ACM, whichever is longer.
²Communication Error- If the cluster receives
no airbag messages for six consecutive seconds, the
airbag indicator is illuminated. The indicator
8J - 12 INSTRUMENT CLUSTERKJ
ABS INDICATOR (Continued)

remains illuminated until the cluster receives a sin-
gle lamp-off message from the ACM.
²Actuator Test- Each time the cluster is put
through the actuator test, the airbag indicator will be
turned on, then off again during the bulb check por-
tion of the test to confirm the functionality of the
LED and the cluster control circuitry. The actuator
test illumination of the airbag indicator is a function
of the instrument cluster.
The ACM continually monitors the airbag system
circuits and sensors to decide whether the system is
in good operating condition. The ACM then sends the
proper lamp-on or lamp-off messages to the instru-
ment cluster. If the ACM sends a lamp-on message
after the bulb test, it indicates that the ACM has
detected a system malfunction and/or that the air-
bags and driver seat belt tensioner may not deploy
when required, or may deploy when not required.
The ACM will store a Diagnostic Trouble Code (DTC)
for any malfunction it detects. Each time the airbag
indicator fails to illuminate due to an open or short
in the cluster airbag indicator circuit, the cluster
sends a message notifying the ACM of the condition,
then the instrument cluster and the ACM will each
store a DTC. For proper diagnosis of the airbag sys-
tem, the ACM, the PCI data bus, or the message
inputs to the instrument cluster that control the air-
bag indicator, a DRBIIItscan tool is required. Refer
to the appropriate diagnostic information.
BRAKE/PARK BRAKE
INDICATOR
DESCRIPTION
A brake indicator is standard equipment on all
instrument clusters. The brake indicator is located
near the lower edge of the tachometer dial face in the
instrument cluster. The brake indicator consists of
stencil-like cutouts of the word ªBRAKEº and the
International Control and Display Symbol icon for
ªBrake Failureº in the opaque layer of the instru-
ment cluster overlay. The dark outer layer of the
overlay prevents the indicator from being clearly vis-
ible when it is not illuminated. A red Light Emitting
Diode (LED) behind the cutout in the opaque layer of
the overlay causes the ªBRAKEº text and the icon to
appear in red through the translucent outer layer of
the overlay when the indicator is illuminated from
behind by the LED, which is soldered onto the
instrument cluster electronic circuit board. The brake
indicator is serviced as a unit with the instrument
cluster.
OPERATION
The brake indicator gives an indication to the vehi-
cle operator when the parking brake is applied, when
there are certain brake hydraulic system malfunc-
tions as indicated by a low brake hydraulic fluid level
condition, or when the brake fluid level switch is dis-
connected. On models equipped with an optional
Antilock Brake System (ABS), the brake indicator
can also give an indication when certain faults are
detected in the ABS. This indicator is controlled by a
transistor on the instrument cluster electronic circuit
board based upon cluster programming, electronic
messages received by the cluster from the Controller
Antilock Brake (CAB) over the Programmable Com-
munications Interface (PCI) data bus (ABS only), and
hard wired inputs from the park brake switch and
the brake fluid level switch. The brake indicator
Light Emitting Diode (LED) is completely controlled
by the instrument cluster logic circuit, and that logic
will only allow this indicator to operate when the
instrument cluster receives a battery current input
on the fused ignition switch output (run-start) cir-
cuit. Therefore, the LED will always be off when the
ignition switch is in any position except On or Start.
The LED only illuminates when it is provided a path
to ground by the instrument cluster transistor. The
instrument cluster will turn on the brake indicator
for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the brake indicator is illu-
minated by the instrument cluster for about three
seconds as a bulb test.
²Brake Lamp-On Message- Each time the
cluster receives a lamp-on message from the CAB,
the brake indicator will be illuminated. The indicator
remains illuminated until the cluster receives a
lamp-off message from the CAB, or until the ignition
switch is turned to the Off position, whichever occurs
first.
²Park Brake Switch Input- Each time the
cluster detects ground on the park brake switch
sense circuit (park brake switch closed = park brake
applied or not fully released) the brake indicator is
illuminated. The indicator remains illuminated until
the park brake switch sense input to the cluster is an
open circuit (park brake switch open = park brake
fully released), or until the ignition switch is turned
to the Off position, whichever occurs first.
²Brake Fluid Level Switch Input- Each time
the cluster detects ground on the red brake warning
indicator driver circuit (brake fluid level switch
closed = brake hydraulic system fluid level low) the
brake indicator is illuminated solid. The indicator
remains illuminated until the status of the red brake
warning indicator driver input to the cluster is off
(brake fluid level switch off = brake hydraulic system
KJINSTRUMENT CLUSTER 8J - 13
AIRBAG INDICATOR (Continued)

fluid level is not low), or until the ignition switch is
turned to the Off position, whichever occurs first.
²Brake Fluid Level Switch Input Fault- The
brake fluid level switch also features a 1 kilohm
diagnostic resistor connected in parallel between the
switch input and output to provide the cluster with
verification that the red brake warning indicator
driver circuit is not open. If the cluster does not see a
proper input on the red brake warning indicator
driver circuit, it will turn on the brake indicator. The
indicator remains illuminated until the red brake
warning indicator driver circuit fault is resolved, or
until the ignition switch is turned to the Off position,
whichever occurs first.
²Actuator Test- Each time the instrument clus-
ter is put through the actuator test, the brake indi-
cator will be turned on, then off again during the
bulb check portion of the test to confirm the function-
ality of the LED and the cluster control circuitry.
The park brake switch on the park brake pedal
mechanism provides a hard wired ground input to
the instrument cluster circuitry through the park
brake switch sense circuit whenever the park brake
is applied or not fully released. The brake fluid level
switch on the brake master cylinder reservoir pro-
vides a hard wired ground input to the instrument
cluster circuitry through the red brake warning indi-
cator driver circuit whenever the fluid level in the
reservoir becomes low. On models equipped with the
optional ABS, the CAB sends the proper lamp-on or
lamp-off messages to the instrument cluster. If the
CAB sends a lamp-on message after the bulb test, it
indicates that the CAB has detected a brake hydrau-
lic system malfunction and/or that the ABS system
has become inoperative. The CAB will store a Diag-
nostic Trouble Code (DTC) for any malfunction it
detects.
For further diagnosis of the brake indicator or the
instrument cluster circuitry that controls the LED,
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). The park brake
switch input to the instrument cluster can be diag-
nosed using conventional diagnostic tools and meth-
ods. For proper diagnosis of the brake fluid level
switch input to the instrument cluster, the antilock
brake system, the CAB, the PCI data bus, or the
electronic message inputs to the instrument cluster
that control the brake indicator, a DRBIIItscan tool
is required. Refer to the appropriate diagnostic infor-
mation.
DIAGNOSIS AND TESTING - BRAKE INDICATOR
The diagnosis found here addresses an inoperative
brake indicator condition. If there are problems with
several indicators in the instrument cluster, (Refer to
8 - ELECTRICAL/INSTRUMENT CLUSTER - DIAG-NOSIS AND TESTING). If the brake indicator stays
on with the ignition switch in the On position and
the park brake released, or comes on while driving,
(Refer to 5 - BRAKES - DIAGNOSIS AND TEST-
ING). If no brake system problem is found, the fol-
lowing procedures will help to locate a shorted or
open circuit, or a faulty park brake switch input.
Refer to the appropriate wiring information. The wir-
ing information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
harness routing and retention, connector pin-out
information and location views for the various wire
harness connectors, splices and grounds.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
INDICATOR ILLUMINATES DURING BULB TEST, BUT DOES
NOT WHEN PARK BRAKE APPLIED
(1) Disconnect and isolate the battery negative
cable. Disconnect the front body wire harness connec-
tor for the park brake switch from the switch termi-
nal. Apply the parking brake. Check for continuity
between the park brake switch terminal and a good
ground. There should be continuity. If OK, go to Step
2. If not OK, replace the faulty park brake switch.
(2) Disconnect the instrument panel wire harness
connector for the instrument cluster from the cluster
connector receptacle. Check for continuity between
the park brake switch sense circuit cavities of the
front body wire harness connector for the park brake
switch and the instrument panel wire harness con-
nector for the instrument cluster. There should be
continuity. If not OK, repair the open park brake
switch sense circuit between the park brake switch
and the instrument cluster as required.
INDICATOR REMAINS ILLUMINATED - BRAKE SYSTEM
CHECKS OK
(1) Disconnect and isolate the battery negative
cable. Disconnect the front body wire harness connec-
8J - 14 INSTRUMENT CLUSTERKJ
BRAKE/PARK BRAKE INDICATOR (Continued)

tor for the park brake switch from the switch termi-
nal. Check for continuity between the terminal of the
park brake switch and a good ground. There should
be no continuity with the park brake released, and
continuity with the park brake applied. If OK, go to
Step 2. If not OK, replace the faulty park brake
switch.
(2) Disconnect the instrument panel wire harness
connector for the instrument cluster from the cluster
connector receptacle. Check for continuity between
the park brake switch sense circuit cavity of the front
body wire harness connector for the park brake
switch and a good ground. There should be no conti-
nuity. If not OK, repair the shorted park brake
switch sense circuit between the park brake switch
and the instrument cluster as required.
CHARGING INDICATOR
DESCRIPTION
A charging indicator is standard equipment on all
instrument clusters. The charging indicator is located
above the engine temperature gauge and to the right
of the speedometer in the instrument cluster. The
charging indicator consists of a stencil-like cutout of
the International Control and Display Symbol icon
for ªBattery Charging Conditionº in the opaque layer
of the instrument cluster overlay. The dark outer
layer of the overlay prevents the indicator from being
clearly visible when it is not illuminated. A red Light
Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes the icon to appear
in red through the translucent outer layer of the
overlay when the indicator is illuminated from
behind by the LED, which is soldered onto the
instrument cluster electronic circuit board. The
charging indicator is serviced as a unit with the
instrument cluster.
OPERATION
The charging indicator gives an indication to the
vehicle operator when the electrical system voltage is
too low or too high. This indicator is controlled by a
transistor on the instrument cluster electronic circuit
board based upon the cluster programming and elec-
tronic messages received by the cluster from the
Powertrain Control Module (PCM) over the Program-
mable Communications Interface (PCI) data bus. The
charging indicator Light Emitting Diode (LED) is
completely controlled by the instrument cluster logic
circuit, and that logic will only allow this indicator to
operate when the instrument cluster receives a bat-
tery current input on the fused ignition switch out-
put (run-start) circuit. Therefore, the LED will
always be off when the ignition switch is in any posi-tion except On or Start. The LED only illuminates
when it is provided a path to ground by the instru-
ment cluster transistor. The instrument cluster will
turn on the charging indicator for the following rea-
sons:
²Bulb Test- Each time the ignition switch is
turned to the On position the charging indicator is
illuminated by the instrument cluster for about three
seconds as a bulb test.
²Charge Fail Message- Each time the cluster
receives a charge fail message from the PCM (system
voltage is nine volts or lower, the charging indicator
will be illuminated. The indicator remains illumi-
nated until the cluster receives a message from the
PCM indicating there is no charge fail condition (sys-
tem voltage is twelve volts or higher, but lower than
sixteen volts), or until the ignition switch is turned to
the Off position, whichever occurs first.
²Voltage High Message- Each time the cluster
receives a message from the PCM indicating a volt-
age high condition (system voltage is sixteen volts or
higher), the lamp will be illuminated. The lamp
remains illuminated until the cluster receives a mes-
sage from the PCM indicating there is no voltage
high condition (system voltage is lower than sixteen
volts, but higher than nine volts), or until the igni-
tion switch is turned to the Off position, whichever
occurs first.
²Actuator Test- Each time the cluster is put
through the actuator test, the charging indicator will
be turned on, then off again during the bulb check
portion of the test to confirm the functionality of the
LED and the cluster control circuitry.
The PCM continually monitors the electrical sys-
tem voltage to control the generator output. The
PCM then sends the proper system voltage messages
to the instrument cluster. If the instrument cluster
turns on the indicator after the bulb test, it may
indicate that the charging system requires service.
For further diagnosis of the charging indicator or the
instrument cluster circuitry that controls the indica-
tor, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). For
proper diagnosis of the charging system, the PCI
data bus, or the electronic message inputs to the
instrument cluster that control the charging indica-
tor, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
COOLANT LOW INDICATOR
DESCRIPTION
A coolant low indicator is only found in the instru-
ment clusters of vehicles equipped with an optional
diesel engine. The coolant low indicator is located
KJINSTRUMENT CLUSTER 8J - 15
BRAKE/PARK BRAKE INDICATOR (Continued)