2002 JEEP LIBERTY check engine

NOTE: Over or under tightening the sensor mount-
ing bolts will affect knock sensor performance, pos-
sibly causing improper spark control. Always use
the specified torque when installing the knock sen-
sors.
REMOVAL
The 2 knock sensors are bolted into the cylinder
block under the intake manifold (Fig. 20).
NOTE: The left sensor is identified by an identifica-
tion tag (LEFT). It is also identified by a larger bolt
head. The Powertrain Control Module (PCM) must
have and know the correct sensor left/right posi-
tions. Do not mix the sensor locations.
(1) Disconnect knock sensor dual pigtail harness
from engine wiring harness. this connection is made
near rear of left valve cover (Fig. 20).
(2) Remove intake manifold. Refer to Engine sec-
tion.
(3) Remove sensor mounting bolts (Fig. 20). Note
foam strip on bolt threads. This foam is used only to
retain the bolts to sensors for plant assembly. It is
not used as a sealant. Do not apply any adhesive,
sealant or thread locking compound to these bolts.
(4) Remove sensors from engine.
INSTALLATION
NOTE: The left sensor is identified by an identifica-
tion tag (LEFT). It is also identified by a larger bolt
head. The Powertrain Control Module (PCM) must
have and know the correct sensor left/right posi-
tions. Do not mix the sensor locations.
(1) Thoroughly clean knock sensor mounting holes.
(2) Install sensors into cylinder block.
NOTE: Over or under tightening the sensor mount-
ing bolts will affect knock sensor performance, pos-
sibly causing improper spark control. Always use
the specified torque when installing the knock sen-
sors. The torque for the knock senor bolt is rela-
tively light for an 8mm bolt.
NOTE: Note foam strip on bolt threads. This foam is
used only to retain the bolts to sensors for plant
assembly. It is not used as a sealant. Do not apply
any adhesive, sealant or thread locking compound
to these bolts.
(3) Install and tighten mounting bolts. Refer to
torque specification.
(4) Install intake manifold. Refer to Engine sec-
tion.
(5) Connect knock sensor wiring harness to engine
harness at rear of intake manifold.
SPARK PLUG
DESCRIPTION
Resistor type spark plugs are used.
Spark plug resistance values range from 6,000 to
20,000 ohms (when checked with at least a 1000 volt
spark plug tester).Do not use an ohmmeter to
check the resistance values of the spark plugs.
Inaccurate readings will result.
OPERATION
To prevent possible pre-ignition and/or mechanical
engine damage, the correct type/heat range/number
spark plug must be used.
Always use the recommended torque when tighten-
ing spark plugs. This is especially true when plugs
are equipped with tapered seats. Incorrect torque can
distort the spark plug and change plug gap. It can
also pull the plug threads and do possible damage to
both the spark plug and the cylinder head.
Remove the spark plugs and examine them for
burned electrodes and fouled, cracked or broken por-
celain insulators. Keep plugs arranged in the order
in which they were removed from the engine. A sin-
Fig. 20 KNOCK SENSOR LOCATION
1 - KNOCK SENSORS (2)
2 - MOUNTING BOLTS
8I - 12 IGNITION CONTROLKJ
KNOCK SENSOR (Continued)

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) Before installing coil(s), check condition of coil
o-ring and replace as necessary. To aid in coil instal-
lation, apply silicone to coil o-ring.
(4) Install ignition coil(s). Refer to Ignition Coil
Removal/Installation.
IGNITION COIL CAPACITOR
DESCRIPTION
One coil capacitor is used. It is located in the
engine compartment and attached (clipped) to a wir-
ing trough near the brake power booster.
OPERATION
The coil capacitor(s) help dampen the amount of
conducted electrical noise to the camshaft position
sensor, crankshaft position sensor, and throttle posi-
tion sensor. This noise is generated on the 12V sup-
ply wire to the ignition coils and fuel injectors.
REMOVAL
The coil capacitor is located in the engine compart-
ment and is attached (clipped) to a wiring harness
trough near the brake power booster (graphic not
available).
(1) Unclip capacitor from wiring harness trough.
(2) Disconnect electrical connector at capacitor.
INSTALLATION
(1) Connect electrical connector to coil capacitor.
(2) Position capacitor into v-clip on wiring harness
trough.
8I - 16 IGNITION CONTROLKJ
SPARK PLUG (Continued)

fused ignition switch output (run-start) circuit
between the JB and the ignition switch as required.
(6) With the ignition switch still in the On posi-
tion, check for battery voltage at the fused ignition
switch output (run-start) circuit cavity of the instru-
ment panel wire harness connector for the instru-
ment cluster. If OK, go to Step 7. If not OK, repair
the open fused ignition switch output circuit (run-
start) between the instrument cluster and the JB as
required.
(7) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Check for continuity between the ground circuit cav-
ity of the instrument panel wire harness connector
for the instrument cluster and a good ground. There
should be continuity. If OK, refer to ACTUATOR
TEST . If not OK, repair the open ground circuit
between the instrument cluster and ground (G202) as
required.
ACTUATOR TEST
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.
The instrument cluster actuator test will put the
instrument cluster into its self-diagnostic mode. In
this mode the instrument cluster can perform a self-
diagnostic test that will confirm that the instrument
cluster circuitry, the gauges, the PCI data bus mes-
sage controlled indicator lamps, and the chime tone
generator are capable of operating as designed. Dur-
ing the actuator test the instrument cluster circuitry
will sound the chime tone generator, position each of
the gauge needles at various specified calibration
points, illuminate each of the segments in the Vacu-um-Fluorescent Display (VFD), and turn all of the
PCI data bus message-controlled indicators on and
off again.
Successful completion of the actuator test will con-
firm that the instrument cluster is operational. How-
ever, there may still be a problem with the PCI data
bus, the Powertrain Control Module (PCM), the Air-
bag Control Module (ACM), the Sentry Key Immobi-
lizer Module (SKIM), or the inputs to one of these
electronic control modules. Use a DRBIIItscan tool
to diagnose these components. Refer to the appropri-
ate diagnostic information.
(1) Begin the test with the ignition switch in the
Off position.
(2) Depress the odometer/trip odometer switch but-
ton.
(3) While still holding the odometer/trip odometer
switch button depressed, turn the ignition switch to
the On position, but do not start the engine.
(4) Release the odometer/trip odometer switch but-
ton.
(5) The instrument cluster will automatically
begin the actuator test sequence, as follows:
(a) The cluster will turn on, then off again each
of the PCI data bus message controlled indicators
to confirm the functionality of the indicator and
the cluster control circuitry:
(b) The cluster will sweep the needles for each of
the gauges to several calibration points in sequence
to confirm the functionality of the gauge and the
cluster control circuitry:
(c) The cluster will sequentially step the odome-
ter/trip odometer VFD display from all ones
( 111111 )through all nines (999999) to confirm the
functionality of all VFD segments and their control
circuitry, then display the software version number.
(d) The cluster will generate five (5) chime tones
to confirm the functionality of the chime tone gen-
erator and the chime control circuitry.
(6) The actuator test is now completed. The instru-
ment cluster will automatically exit the self-diagnos-
tic mode and return to normal operation at the
completion of the test, if the ignition switch is turned
to the Off position during the test, or if an engine
rpm message indicating that the engine is running is
received from the PCM over the PCI data bus during
the test.
(7) Go back to Step 1 to repeat the test, if
required.
8J - 8 INSTRUMENT CLUSTERKJ
INSTRUMENT CLUSTER (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)

above the fuel gauge and to the left of the tachometer
in the instrument cluster. The coolant low indicator
consists of a stencil-like cutout of the International
Control and Display Symbol icon for ªLow Engine
Coolantº in the opaque layer of the instrument clus-
ter overlay. The dark outer layer of the overlay pre-
vents the indicator from being clearly visible when it
is not illuminated. An amber Light Emitting Diode
(LED) behind the cutout in the opaque layer of the
overlay causes the icon to appear in amber 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 elec-
tronic circuit board. The coolant low indicator is ser-
viced as a unit with the instrument cluster.
OPERATION
The coolant low indicator gives an indication to the
vehicle operator when the diesel engine coolant level
is low. This indicator is controlled by a transistor on
the instrument cluster circuit board based upon clus-
ter programming and a hard wired input received by
the cluster from the engine coolant level switch. The
coolant low 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 coolant low indicator for the following
reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the coolant low indicator is
illuminated for about three seconds as a bulb test.
²Engine Coolant Level Switch Input- Each
time the cluster detects ground on the low coolant
fluid level sense circuit (engine coolant level switch
closed = engine coolant level low) the cluster applies
an algorithm to confirm that the input is correct and
not the result of coolant sloshing in the coolant bot-
tle. The cluster tests the status of the circuit about
seven milliseconds after ignition On, and about once
every second thereafter, then uses an internal
counter to count up or down. When the counter accu-
mulates thirty ground inputs on the circuit, the cool-
ant low indicator will be illuminated. The indicator
remains illuminated until the low coolant fluid level
sense input to the cluster is an open circuit (engine
coolant level switch open = engine coolant level full),
or until the ignition switch is turned to the Off posi-
tion, whichever occurs first.²Engine Coolant Level Switch Input Fault-
The engine coolant level switch also features a 3.3
kilohm diagnostic resistor connected in parallel
between the switch input and output to provide the
cluster with verification that the low coolant fluid
level sense circuit is not open or shorted. If the clus-
ter does not see a proper input on the low coolant
fluid level sense circuit, it will suspend coolant low
indicator operation. The indicator operation remains
suspended until the low coolant fluid level sense cir-
cuit fault is resolved.
²Actuator Test- Each time the cluster is put
through the actuator test, the coolant low 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 engine coolant level switch on the coolant bot-
tle provides a hard wired ground input to the instru-
ment cluster circuitry through the low coolant fluid
level sense circuit whenever the level of the coolant
in the bottle is low. For further diagnosis of the cool-
ant low indicator or the instrument cluster circuitry
that controls the LED, (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). For proper diagnosis of the engine cool-
ant level switch input to the instrument cluster that
control the coolant low indicator, a DRBIIItscan tool
is required. Refer to the appropriate diagnostic infor-
mation.
CRUISE INDICATOR
DESCRIPTION
A cruise indicator is standard equipment on all
instrument clusters, but is only functional on vehi-
cles equipped with the optional speed control system.
The cruise indicator is located near the lower edge of
the instrument cluster, between the tachometer and
the speedometer. The cruise indicator consists of a
stencil-like cutout of the word ªCRUISEº 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 green Light Emitting Diode (LED) behind the cut-
out in the opaque layer of the overlay causes the
ªCRUISEº text to appear in green through the trans-
lucent outer layer of the overlay when it is illumi-
nated from behind by the LED, which is soldered
onto the instrument cluster electronic circuit board.
When the exterior lighting is turned On, the illumi-
nation intensity of the cruise indicator is dimmable,
which is adjusted using the panel lamps dimmer con-
trol ring on the left control stalk of the multi-func-
tion switch. The cruise indicator is serviced as a unit
with the instrument cluster.
8J - 16 INSTRUMENT CLUSTERKJ
COOLANT LOW INDICATOR (Continued)

gauge, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
FRONT FOG LAMP INDICATOR
DESCRIPTION
A front fog lamp indicator is standard equipment
on all instrument clusters, but is only functional on
vehicles equipped with the optional front fog lamps.
The front fog lamp indicator is located above the
engine temperature gauge and to the right of the
speedometer in the instrument cluster. The front fog
lamp indicator consists of a stencil-like cutout of the
International Control and Display Symbol icon for
ªFront Fog Lightº 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 green Light Emit-
ting Diode (LED) behind the cutout in the opaque
layer of the overlay causes the icon to appear in
green through the translucent outer layer of the
overlay when it is illuminated from behind by the
LED, which is soldered onto the instrument cluster
electronic circuit board. When the exterior lighting is
turned On, the illumination intensity of the front fog
lamp indicator is dimmable, which is adjusted using
the panel lamps dimmer control ring on the left con-
trol stalk of the multi-function switch. The front fog
lamp indicator is serviced as a unit with the instru-
ment cluster.
OPERATION
The front fog lamp indicator gives an indication to
the vehicle operator whenever the front fog lamps
are illuminated. 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
Body Control Module (BCM) over the Programmable
Communications Interface (PCI) data bus. The front
fog lamp indicator Light Emitting Diode (LED) is
completely controlled by the instrument cluster logic
circuit, and that logic will allow this indicator to
operate whenever the instrument cluster receives a
battery current input on the fused B(+) circuit.
Therefore, the LED can be illuminated regardless of
the ignition switch position. The LED only illumi-
nates when it is provided a path to ground by the
instrument cluster transistor. The instrument cluster
will turn on the front fog lamp indicator for the fol-
lowing reasons:
²Front Fog Lamp-On Message- Each time the
cluster receives a front fog lamp-on message from the
BCM indicating the front fog lamps are turned On,
the front fog lamp indicator will be illuminated. Theindicator remains illuminated until the cluster
receives a front fog lamp-off message from the BCM.
²Actuator Test- Each time the cluster is put
through the actuator test, the front fog lamp 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.
The BCM continually monitors the exterior light-
ing (multi-function) switch to determine the proper
outputs to the front fog lamp relay. The BCM then
sends the proper front fog lamp indicator lamp-on
and lamp-off messages to the instrument cluster. For
further diagnosis of the front fog lamp indicator or
the instrument cluster circuitry that controls the
indicator, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). For
proper diagnosis of the front fog lamp system, the
BCM, the PCI data bus, or the electronic message
inputs to the instrument cluster that control the
front fog lamp indicator, a DRBIIItscan tool is
required. Refer to the appropriate diagnostic infor-
mation.
FUEL GAUGE
DESCRIPTION
A fuel gauge is standard equipment on all instru-
ment clusters. The fuel gauge is located in the left
lower corner of the instrument cluster, to the left of
the tachometer. The fuel gauge consists of a movable
gauge needle or pointer controlled by the instrument
cluster circuitry and a fixed 90 degree scale on the
cluster overlay that reads left-to-right from E (or
Empty) to F (or Full). An International Control and
Display Symbol icon for ªFuelº is located on the clus-
ter overlay, in the center of the gauge directly above
the hub of the gauge needle. An arrowhead pointed
to the left side of the vehicle is imprinted on the clus-
ter overlay next to the ªFuelº icon in the fuel gauge
to provide the driver with a reminder as to the loca-
tion of the fuel filler access. The fuel gauge graphics
are dark blue and black against a beige field, except
for a single red graduation at the far left (Empty)
end of the gauge scale, making them clearly visible
within the instrument cluster in daylight. When illu-
minated from behind by the panel lamps dimmer
controlled cluster illumination lighting with the exte-
rior lamps turned On, the blue graphics appear blue
and the red graphics appear red. The orange gauge
needle is internally illuminated. Gauge illumination
is provided by replaceable incandescent bulb and
bulb holder units located on the instrument cluster
electronic circuit board. The fuel gauge is serviced as
a unit with the instrument cluster.
KJINSTRUMENT CLUSTER 8J - 19
ENGINE TEMPERATURE GAUGE (Continued)

when it is provided a path to ground by the instru-
ment cluster transistor. The instrument cluster will
turn on the low fuel indicator for the following rea-
sons:
²Bulb Test- Each time the ignition switch is
turned to the On position the low fuel indicator is
illuminated for about three seconds as a bulb test.
²Less Than 12.5 Percent Tank Full Message-
Each time the cluster receives a message from the
PCM indicating that the percent tank full is less
than 12.5 (one-eighth), the low fuel indicator is illu-
minated. The indicator remains illuminated until the
cluster receives messages from the PCM indicating
that the percent tank full has increased to greater
than 12.5 (one-eighth). The PCM applies an algo-
rithm to the input from the fuel tank sender to
dampen the illumination of the low fuel indicator
against the negative effect that fuel sloshing within
the fuel tank can have on accurate inputs to the
PCM.
²Less Than Empty Percent Tank Full Mes-
sage- Each time the cluster receives a message from
the PCM indicating the percent tank full is less than
empty, the low fuel indicator is illuminated immedi-
ately. This message would indicate that the fuel tank
sender input to the PCM is a short circuit.
²More Than Full Percent Tank Full Message
- Each time the cluster receives a message from the
PCM indicating the percent tank full is more than
full, the low fuel indicator is illuminated immedi-
ately. This message would indicate that the fuel tank
sender input to the PCM is an open circuit.
²Communication Error- If the cluster fails to
receive a percent tank full message for more than
about twelve seconds, the cluster control circuitry
will illuminate the low fuel indicator until a new per-
cent tank full message is received, 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 low fuel 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 fuel tank
sender input to determine the fuel level. The PCM
then applies an algorithm to the input and sends the
proper percent tank full messages to the instrument
cluster. For further diagnosis of the low fuel indicator
or the instrument cluster circuitry that controls the
LED, (Refer to 8 - ELECTRICAL/INSTRUMENT
CLUSTER - DIAGNOSIS AND TESTING). For
proper diagnosis of the fuel tank sender, the PCM,
the PCI data bus, or the electronic message inputs to
the instrument cluster that control the low fuel indi-cator, a DRBIIItscan tool is required. Refer to the
appropriate diagnostic information.
LOW OIL PRESSURE
INDICATOR
DESCRIPTION
A low oil pressure indicator is standard equipment
on all instrument clusters. The low oil pressure indi-
cator is located near the lower edge of the instrument
cluster, between the tachometer and the speedometer.
The low oil pressure indicator consists of a stencil-
like cutout of the International Control and Display
Symbol icon for ªEngine Oilº 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 it is illuminated from behind by the
LED, which is soldered onto the instrument cluster
electronic circuit board. The low oil pressure indica-
tor is serviced as a unit with the instrument cluster.
OPERATION
The low oil pressure indicator gives an indication
to the vehicle operator when the engine oil pressure
is low. This indicator is controlled by a transistor on
the instrument cluster electronic circuit board based
upon cluster programming and electronic messages
received by the cluster from the Powertrain Control
Module (PCM) over the Programmable Communica-
tions Interface (PCI) data bus. The low oil pressure
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 cur-
rent input on the fused ignition switch output (run-
start) circuit. 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 pro-
vided a path to ground by the instrument cluster
transistor. The instrument cluster will turn on the
low oil pressure indicator for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the low oil pressure indica-
tor is illuminated as a bulb test. The indicator will
remain illuminated until the engine is started
(engine speed is greater than 450 rpm), or until the
ignition switch is turned to the Off position, which-
ever occurs first.
²Engine Oil Pressure Low Message- Once the
engine has been started (engine speed has been
greater than 450 rpm), each time the cluster receives
KJINSTRUMENT CLUSTER 8J - 23
LOW FUEL INDICATOR (Continued)

three consecutive messages from the PCM indicating
that the engine oil pressure is about 4 kPa or lower
(about 0.6 psi or lower), the low oil pressure indicator
is illuminated. The indicator remains illuminated
until the cluster receives a single message from the
PCM indicating that the engine oil pressure is about
76 kPa or higher (about 11 psi or higher), or until the
ignition switch is turned to the Off position, which-
ever occurs first. Once the cluster monitors and
engine speed of greater than 450 rpm, the cluster
logic will ignore engine speed in determining low oil
pressure indicator operation for the remainder of the
current ignition cycle.
²Actuator Test- Each time the cluster is put
through the actuator test, the low oil pressure 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 PCM continually monitors the engine oil pres-
sure sensor to determine the engine oil pressure. The
PCM then sends the proper engine oil pressure mes-
sages to the instrument cluster. For further diagnosis
of the low oil pressure indicator or the instrument
cluster circuitry that controls the LED, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNO-
SIS AND TESTING). If the instrument cluster turns
on the indicator after the bulb test, it may indicate
that the engine or the engine oiling system requires
service. For proper diagnosis of the engine oil pres-
sure sensor, the PCM, the PCI data bus, or the elec-
tronic message inputs to the instrument cluster that
control the low oil pressure indicator, a DRBIIItscan
tool is required. Refer to the appropriate diagnostic
information.
MALFUNCTION INDICATOR
LAMP (MIL)
DESCRIPTION
A Malfunction Indicator Lamp (MIL) is standard
equipment on all instrument clusters. The MIL is
located above the coolant temperature gauge and to
the right of the speedometer in the instrument clus-
ter. The MIL consists of a stencil-like cutout of the
International Control and Display Symbol icon for
ªEngineº in the opaque layer of the instrument clus-
ter overlay. The dark outer layer of the overlay pre-
vents the indicator from being clearly visible when it
is not illuminated. An amber Light Emitting Diode
(LED) behind the cutout in the opaque layer of the
overlay causes the icon to appear in amber through
the translucent outer layer of the overlay when it is
illuminated from behind by the LED, which is sol-
dered onto the instrument cluster electronic circuitboard. The MIL is serviced as a unit with the instru-
ment cluster.
OPERATION
The Malfunction Indicator Lamp (MIL) gives an
indication to the vehicle operator when the Power-
train Control Module (PCM) has recorded a Diagnos-
tic Trouble Code (DTC) for an On-Board Diagnostics
II (OBDII) emissions-related circuit or component
malfunction. This indicator is controlled by a transis-
tor on the instrument cluster electronic circuit board
based upon cluster programming and electronic mes-
sages received by the cluster from the PCM over the
Programmable Communications Interface (PCI) data
bus. The MIL Light Emitting Diode (LED) is com-
pletely controlled by the instrument cluster logic cir-
cuit, 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 MIL for the following reasons:
²Bulb Test- Each time the ignition switch is
turned to the On position the MIL is illuminated for
about seven seconds as a bulb test.
²PCM Lamp-On Message- Each time the clus-
ter receives a malfunction indicator lamp-on message
from the PCM, the indicator will be illuminated. The
indicator can be flashed on and off, or illuminated
solid, as dictated by the PCM message. For some
DTC's, if a problem does not recur, the PCM will
send a lamp-off message automatically. Other DTC's
may require that a fault be repaired and the PCM be
reset before a lamp-off message will be sent. For
more information on the PCM and the DTC set and
reset parameters, (Refer to 25 - EMISSIONS CON-
TROL - OPERATION).
²Communication Error- If the cluster receives
no malfunction indicator lamp-on or lamp-off mes-
sage from the PCM for twenty consecutive seconds,
the MIL is illuminated by the instrument cluster.
The indicator remains controlled and illuminated by
the cluster until a valid malfunction indicator
lamp-on or lamp-off message is received from the
PCM.
²Actuator Test- Each time the cluster is put
through the actuator test, the MIL 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 each of the many
fuel and emissions system circuits and sensors to
decide whether the system is in good operating con-
8J - 24 INSTRUMENT CLUSTERKJ
LOW OIL PRESSURE INDICATOR (Continued)