Instrument Cluster

INSTRUMENT CLUSTER
The instrument cluster for Jeep Cherokee (XJ) is available for two different versions: base with two gauges and premium with six gauges. The gauges are positioned with information received by the cluster over the CCD bus from the PCM. Some of the warming lamps are hardwired and some are controlled by the cluster using CCD bus information. The vehicle chime function is contained on the cluster circuit board, as well as the timer for the rear window defogger. There is a self-test available for the cluster that will actuate all the gauges and place them at their calibration points. The test will not run if the cluster sees engine RPM or vehicle speed. This test will light all CCD controlled lamps for verification of lamp operation. It also forces the odometer Vacuum Fluorescent Display (VFD) to count up from all zero's through all nine's. The self-test routine can be entered by pushing and holding the trip reset button while rotating the ignition key from the "OFF" to the "ON" position, release the button after the test starts.

The VFD is also capable of displaying PCM DTC's. This feature is accessed the same as in previous years by turning they key from "OFF" to "RUN" three times and staying in the "RUN" position.

The instrument cluster will provide bus bias and termination and the PCM controller provides a second termination. If cluster is disconnected, the bus will not be biased.

The cluster will be serviced as an assembly. There will be limited parts available: bulbs and sockets, the front lens, the trip odometer stem cover and the hood and rear cover assembly. No internal parts of the lowline or highline cluster will be serviced.

Normal Operation: At key "ON", the cluster will light the low fuel, oil pressure, temperature battery, seat belt, check gauges and airbag lamps. The check engine, ABS, and SKIM lamps are bulb tested by their system modules. As the key is turned farther toward the start position, the brake warning lamp will illuminate. The Vacuum Fluorescent Display (VFD) will indicate the mileage stored inside the cluster. If there is a bus failure and the cluster cannot receive distance pulses from the engine controller, the cluster will display the last mileage stored until the ignition key is turned OFF. If the cluster is receiving bus messages, but is unable to display odometer information because of an internal failure, the odometer display dashes. VFD dimming is handled by the potentiometer that controls instrumentation illumination.

Chime
The chime function is a 1000 Hz tone within the cluster. The cluster will not generate more than one chime per condition in the same ignition cycle. If a problem occurs that requires a second chime while the first one is currently being generated, the second chime request will be ignored. The chime will sound for the following conditions:

- Headlamps ON and driver's door open
- Seat Belt Warning - six seconds after key ON
- Key in Ignition Warning - Driver's front door open with key in ignition
- Engine Temp High - When gauges enter red zone Low Fuel - When fuel reaches 1/8 of a tank
- When overhead console is reset
- SKIM key successfully programmed

Lamps (Hardwired)
The following lamps are hardwired to the cluster and are not part of the self-test:
- Brake Warning (Red) - bulb test performed when the ignition switch is turned to the CRANK position
- Full time 4WD
- Part time 4WD High Beam
- Left Turn Signal Liftgate Ajar

The following lamps are bulb tested at ignition ON by the appropriate system module.
- ABS (Amber)
- Check engine
- SKIM

Lamps (CCD)
The following lamps are controlled by the cluster via CCD messages. They are bulb tested (actuated) during the self-test procedure:
- Airbag
- Cruise Control
- Low Fuel Warning
- Low Washer Fluid
- Upshift (If equipped)
- Seat Belt
- Sentry Key Immobilizer
- Engine Temp (If equipped)
- Battery (If equipped)
- Low Oil Pressure Warning (If equipped)

The lowline cluster does not contain a Check Gauges telltale.

NOTE: THE SEAT BELT AND LOW WASHER FLUID SWITCHES ARE HARDWIRED TO THE CLUSTER. THE CLUSTER THEN DECIDES IF THE LAMP SHOULD ILLUMINATE BASED ON THE HARDWIRED INPUT.

DIAGNOSTICS
Gauges
The Mechanical Instrument Cluster (MIC) will not store any DTCs. Because the Powertrain Control Module (PCM) gathers all the gauge information and sends it to the cluster via the bus, it is the PCM's responsibility to monitor these inputs and store DTCs for them. For this reason, the first item to be checked regarding a gauge problem (except oil pressure) should be the PCM for any DTCs relating to the gauge in question.

There are DTCs associated with all the gauges except for the oil pressure gauge. When diagnosing gauges, the input that is used for the gauge message (fuel level sender, for example) must be valid. Because of OBD II requirements, most of the information used for monitoring the OBD II system is the same information used by the controller to formulate the gauge bus messages. OBD II requirements state the fuel level sender must be checked for rationality. This includes determining if the sending unit voltage is too high or too low, or if the voltage has not changed over time. If the PCM has determined the sender information is not valid, it will set the DTC. The presence or absence of the fuel level sending code in the PCM is an important factor to determine whether a fuel gauge problem is in the sending unit or the cluster.

This same situation is used in all cluster diagnostics related to gauge operation with the exception of the oil pressure gauge. OBD II requirements do not include oil pressure monitoring. Therefore, oil pressure diagnostics would dictate that a mechanical oil pressure gauge be attached to the engine for absolute verification of oil pressure readings.

Hardwired Lamps
The cluster contains several hardwired lamps described earlier. These lamps are set up in two configurations: The lamp is supplied power by the cluster and the ground is supplied by the circuit being monitored, or the lamp is supplied with a ground in the cluster and power comes from a module or other device. Refer to the schematic in General Information for the specific details on the lamp in question. Verification of the bulb filament may be required in all cases of an inoperative lamp. This will require removal of the cluster and bulb in question.

CCD Controlled Lamps
The cluster contains several CCD controlled lamps as described earlier. These lamps are part of the diagnostic self-test. When entering the self-test mode, operation of these lamps can be observed. If the bulb fails to operate during the self-test and the bulb filament is good, the cluster assembly will need to be replaced.