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Home >> Jeep Truck >> 2001 >> Cherokee 4WD RHD L6-4.0L VIN S >> Repair and Diagnosis >> Powertrain Management >> Relays and Modules - Powertrain Management >> Relays and Modules - Computers and Control Systems >> Body Control Module >> Description and Operation >> Functional Operation >> Part 1 of 2 >> Part 1B

Part 1B

Airbag Trouble Codes
The airbag control module may report any of the following diagnostic trouble codes. For the following active or stored codes, replace the Airbag Control Module (ACM):
- AECM Accelerometer
- Internal Diagnostic 1
- Internal Diagnostic 2
- AECM Output Driver
- AECM Stored Energy Logic
- AECM Stored Energy Driver
- AECM Stored Energy Passenger
- Internal Diagnostic 3
- Internal Diagnostic 4
- Safing Sensor Shorted

For these codes, refer to the appropriate diagnostic procedure:
- Driver Squib Circuit Open
- Driver Squib Circuit Shorted
- Loss of Ignition Run Only
- Loss of Ignition Run/Start
- No Cluster CCD Bus Message
- No CCD Communication
- Passenger Squib Circuit Open
- Passenger Squib Circuit Shorted
- Either Squib Term Shorted to Battery
- Either Squib Term Shorted to Ground
- Warning Lamp Circuit Open/Shorted

COMPASS/MINI-TRIP COMPUTER
The Compass/Mini-Trip Computer (CMTC) is in the overhead console. It displays the following information:
- Compass direction
- Current outside temperature
- Elapsed Time (ET)
- Distance To Empty (DTE)
- Average Fuel Economy (AVE ECO)
- Instantaneous Fuel Economy (ECO)
- Trip Odometer (ODO)

All of the information required by the CMTC except the ambient temperature and compass direction is transmitted over the CCD bus.

The CMTC can perform an independent self-test. This can be accomplished by using either the DRB or pressing both US/M and STEP buttons and then turning the ignition key ON. All segments of the CMTC should light while the CMTC checks its internal function. If there are internal failures, the CMTC will display "FAIL." If there is a problem with the CCD communication, the CMTC will display "CCD." Refer to the "Compass/Mini-Trip" for further diagnosis.

Setting The Compass
The compass/mini-trip module is self-calibrated and requires no adjustment. The word CAL will be displayed to indicate that the compass is in the fast calibrating mode. CAL will turn OFF after the vehicle has gone in three complete circles without stopping, in an area free of magnetic disturbance.

If the module displays the temperature while the compass is blank, or displays a false reading, the vehicle must be demagnetized.

If the compass still goes blank after the vehicle is demagnetized, the compass/mini-trip module must be replaced.

Setting The Variance:




Setting The Compass Variance
Variance is the difference between magnetic north and geographic north. To determine the variance for the area you are in, refer to the zone map. The number shown for your area is the variance number for your area.

1. Set the compass/mini-trip console to compass/ temperature mode.
2. Press and hold down both the US/METRIC button and the STEP button for 5 seconds.
3. The VAR light will come ON and the last variance setting will be displayed.
4. Enter the correct variance number by pressing the US/M button.
5. Press the STEP button to set the zone number and resume normal operation.

NOTE: DO NOT ATTACH ANY MAGNETIC DEVICE SUCH AS A MAGNETIC CB ANTENNA TO THE VEHICLE. THIS CAN CAUSE THE COMPASS TO GIVE FALSE READINGS.

INSTRUMENT CLUSTER
The instrument cluster for Jeep Cherokee (XJ) is available in 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 warning 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 (VF) display 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 ignition key cycle.

The VF display is also capable of displaying PCM DTC's, This feature is accessed the same as in previous years by turning the key from "OFF" to "run" three times and staying in 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 (VF) display 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. VF dimming is handled by the potentiometer that controls instrumentation illumination.

Heated Rear Window Defogger
The timing circuit for the rear window defogger is contained in the cluster. The operation is as follows: With the ignition ON, the first push of the defogger button will start a 10-minute timer. After 10 minutes have elapsed, the defogger will be turned OFF. If the button is pushed a second time during the same ignition cycle, the timer will turn the defogger on for five minutes. Every consecutive push will operate the defogger for five minutes. When the defogger is ON, it can be turned OFF with a second push of the defogger button.

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)
Check Gauges

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.

REMOTE KEYLESS ENTRY (RKE)
The Remote Keyless Entry (RKE) module is in the overhead console or in the dome lamp assembly. It operates on a HF signal, which makes it less dependent on the aiming of the transmitter. When an unlock signal is received (from a transmitter), the module will ground the unlock control circuit, therefore actuating the passenger door module and at the same time grounding the courtesy lamps driver circuit, actuating the illuminated entry. The RKE module is capable of retaining four individual vehicle access codes (four transmitters). This system incorporates a rolling code feature. A horn chirp feature is also part of this system and is customer programmable.

The RKE module has some DRB III functions. The Door Lock, Door Unlock, Horn and Illuminated Entry can be actuated. The horn and illuminated entry activation time is adjustable using the DRB III. The DRB III can also turn the horn chirp and illuminated entry ON and OFF.

The XJ will be shipped with the horn chirp enabled. It can be deactivated manually using the following procedure: Press and hold the LOCK button on the transmitter for 5-10 seconds, and then while the LOCK button is pressed, press and release the UNLOCK button. The horn chirp feature can be reactivated by repeating the procedure.

Programming An RKE Transmitter
Programming a transmitter can be accomplished using the DRB III. Using the DRB III select "Theft Alarm," "VTSS" (even though "Vehicle Theft Security System" is not available for this vehicle) then "Miscellaneous" then "Programming RKE". Select a transmitter (1 - 4). The locks will cycle to verify you are in programming mode. Press the unlock button on the transmitter. The locks will cycle again to verify programming has taken place. When you program to a position, that code will overwrite the code that was in that position and because you have no way of knowing if a valid code was there or not, it is recommended that whenever it is necessary to program a transmitter, all transmitters that are to be used with that vehicle should be programmed at that time.

Synchronization (Rolling Code) Button Transmitters
The transmitter will go out of synchronization if the button is pressed more than 128 times outside of the range of the receiver. In other words the transmitter will not unlock the doors. The transmitter will go out of synchronization if the batteries are removed and replaced. To synchronize the code of the particular transmitter with the receiver, press and hold the "lock" button while within the receiver range.
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