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Home >> Jeep >> 2001 >> TJ (CANADA) L6-4.0L >> Repair and Diagnosis >> Instrument Panel, Gauges and Warning Indicators >> Instrument Cluster / Carrier >> Description and Operation >> Instrument Cluster >> Part 5 of 5

Part 5 of 5

SMART CLUSTER FEATURES
The Electro/Mechanical Instrument Cluster houses the Fuel, Voltmeter, Engine Coolant Temp, and Oil Pressure gauges, the Speedometer and the Tachometer. The cluster positions the analog gauges using PCI Bus messages received from the PCM. The cluster also contains 11 (eleven) warning indicators as well as indicators for the Right and Left turn signals and the High Beam headlamps. Some of the indicators are hardwired to the cluster and some indicators are controlled by messages received on the PCI Bus. The vehicle Chime function, Courtesy Lamp Output, the Battery Saver function, and the Rear Window Defogger timer are contained internally within the cluster. The cluster contains a vacuum fluorescent (VF) display for the Odometer/Trip function. The cluster VF will also display P-codes and vehicle status messages. The cluster has the ability to store DTCs, communicate on the PCI Bus, display engine information, and display certain inputs using the DRB III. The cluster is also able to perform a manual self-test.

Normal Operation
As the ignition switch is rotated to the on position, the cluster will illuminate the Low Fuel, Seat Belt, Check Gauges, Airbag, SKIM, and Upshift (if equipped with a manual transmission) indicators. As the ignition switch is rotated towards the start position, the cluster will illuminate the Brake and ABS (if equipped) indicators The vacuum fluorescent (VF) display will indicate the last selected mode, either Odometer or Trip. The Odometer will remain in the last mode selected, Odometer or Trip, after each ignition cycle.

Instrument Cluster Self Test
The Instrument Cluster is capable of performing a manual self test. The self test is actuated by depressing and holding the trip reset button while turning the ignition from the off to the on position. The self test will terminate if the tachometer is greater than 300 RPM, the ignition is turned off or the test is complete. The cluster will perform the self test in the following manner:
1. Chime once.
2. Scroll an "8" across the VF.
3. Illuminate the VF decimal point.
4. Display the cluster software level (example: SOF 8.9).
5. Display the last 6 (six) digits of the Vehicle Identification Number (VIN).
6. Display fault codes in the VF display if set or scroll "no FAULTS" if no faults are set.
- ACM - Air Bag Message = bus b8.
- Indicator Open/Short = Airbag
- Panel Sense - Open Circuit PanEL OPEn.
- PCM - MIL Message = bus b0.
- SKIM - SKIM Message = bus b1.
7. Illuminate all applicable indicators.
- Brake Warning
- Check Gauges
- Cruise
- High Beam
- Low Fuel Warning
- MIL (Malfunction Indicator Lamp)
- Part Time Seat Belt
- SKIM
- Upshift
8. Display Speedometer Calibration Points.
9. Display Fuel Gauge Calibration Points.
10. Display Temperature Gauge Calibration Points.
11. Display Tachometer Calibration Points.
12. Display Volt Gauge Calibration Points.
13. Display Oil Gauge Calibration Points.

DTC Capabilities
The Instrument Cluster is capable of storing diagnostic trouble codes (DTC) and will communicate with the DRB III to display codes. The cluster has the ability to set DTCs for internal cluster failure, lack of communication with other modules, Air Bag Lamp circuit failure, and Panel Dimmer circuit failure.

If the cluster failure is a gauge or meter concern, DTCs will be stored by the PCM. Because the Instrument Cluster receives gauge and meter information from the PCM over the PCI Bus, it is the PCM's function to monitor these inputs and to store DTCs. For this reason the PCM DTCs should be checked first for any condition regarding a gauge problem, except for the Oil Pressure gauge.

There are DTCs associated with all the gauges except for the Oil Pressure gauge. The cluster receives oil pressure information from the PCM over the PCI Bus, but the PCM does not create DTCs for any oil pressure concerns. When diagnosing a gauge concern, 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 PCM to generate the PCI Bus gauge messages. OBD TI requirements state that the fuel level sender must be checked for rationality. This includes determining if the fuel sending unit voltage is too high or too low or if the voltage hasn't changed over time. If the PCM has determined that the sender information isn't valid, it will set a DTC. The presence or absence of a fuel level sending code in the PCM is an important factor to determine whether a fuel gauge problem is in the sending unit or in 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 verification of oil pressure readings.
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