Jeep Cherokee

 Service Manual

Instrument panel systems » Description and operation
Instrument cluster

DESCRIPTION

Two basic instrument clusters are offered on this model: low-line, or high-line. Both clusters are electromechanical units that utilize integrated circuitry and information carried on the Chrysler Collision Detection (CCD) data bus network for control of all gauges and many of the indicator lamps. These clusters also incorporate a digital Vacuum Fluorescent Display (VFD) for the odometer/trip odometer display functions. Some variations of each cluster exist due to optional equipment and regulatory requirements.

The low-line cluster includes the following analog gauges:

•  Fuel gauge
•  Speedometer.

This cluster also includes provisions for the following indicator lamps:

•  Airbag indicator lamp
•  Anti-lock brake system lamp
•  Brake warning lamp
•  Coolant temperature warning lamp
•  Cruise-on indicator lamp
•  Four-wheel drive (Part Time and/or Full Time) indicator lamps
•  Headlamp high beam indicator lamp
•  Low oil pressure warning lamp
•  Low washer fluid warning lamp
•  Malfunction Indicator Lamp (MIL)
•  Seat belt reminder lamp
•  Sentry Key Immobilizer System (SKIS) indicator lamp
•  Turn signal indicator lamps
•  Upshift indicator lamp (manual transmission)
•  Voltage warning lamp.

The high-line cluster replaces some of the indicator lamps found in the low-line cluster with analog gauges. The high-line cluster includes the following analog gauges:

•  Coolant temperature gauge
•  Fuel gauge
•  Oil pressure gauge
•  Speedometer
•  Tachometer
•  Voltmeter.

The high-line cluster also adds a check gauges lamp and a low fuel warning lamp to the remaining indicator lamps found in the low-line cluster.

Both instrument clusters feature circuitry that has a self-diagnostic actuator test capability, which will test each of the CCD bus message-controlled functions of the cluster by lighting the appropriate indicator lamps and positioning the gauge needles at several predetermined locations on the gauge faces in a prescribed sequence. For more information on this function, refer to Instrument Cluster in the Diagnosis and Testing section of this group.

The instrument cluster circuitry also integrates a chime tone generator and a timer circuit. These items replace the chime or buzzer module, and the separate timer circuit for the rear window defogger system. Refer to Chime Warning System in the Description and Operation section of Group 8U - Chime/Buzzer Warning Systems for more information on the chime functions of the instrument cluster.

Refer to Rear Window Defogger System in the Description and Operation section of Group 8N - Electrically Heated Systems for more information on the timer function of the instrument cluster.

The instrument clusters for this model are serviced only as complete units. If a cluster gauge or the cluster circuit board are faulty, the entire cluster must be replaced. The cluster lens, the cluster hood and mask, the rear cluster housing cover, the odometer reset knob boot and the incandescent lamp bulbs and holders are available for service replacement.

OPERATION

GAUGE

With the ignition switch in the On or Start positions, voltage is supplied to all gauges through the instrument cluster electronic circuit board. With the ignition switch in the Off position, voltage is not supplied to the gauges. The gauges do not accurately indicate any vehicle condition unless the ignition switch is in the On or Start positions.

All of the instrument cluster gauges, except the odometer, are air core magnetic units. Two fixed electromagnetic coils are located within the 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 shaft. 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 instrument cluster electronic circuitry in response to messages received on the Chrysler Collision Detection (CCD) data bus network.

The gauge needle moves as the movable permanent magnet aligns itself to the changing magnetic fields created around it by the electromagnets. The instrument cluster circuitry is programmed to move all of the gauge needles back to the low end of their respective scales after the ignition switch is turned to the Off position.

INDICATOR LAMP

Indicator lamps are located in the instrument cluster and are served by the cluster circuit board and connectors. Many of the indicator lamps in the instrument cluster are controlled by the instrument cluster circuitry in response to messages received over the Chrysler Collision Detection (CCD) data bus network.

The anti-lock brake system lamp, brake warning lamp, four-wheel drive indicator lamps, headlamp high beam indicator lamp, low washer fluid warning lamp and turn signal indicator lamps are hard wired.

The seat belt reminder lamp is controlled by the instrument cluster programming. The Malfunction Indicator Lamp (MIL) is normally controlled by CCD data bus messages from the Powertrain Control Module (PCM); however, if the instrument cluster detects a loss of CCD data bus communication, the cluster will automatically turn the MIL on and display the message "NO BUS" in the odometer VFD until CCD data bus communication is restored. The instrument cluster circuitry uses CCD data bus messages from the Powertrain Control Module (PCM), Airbag Control Module (ACM), and the Sentry Key Immobilizer Module (SKIM) to control all of the remaining indicator lamps.

Each of the indicator lamps in the instrument cluster uses incandescent bulbs and holders, which are available for service replacement.

CLUSTER ILLUMINATION LAMP

The cluster illumination lamps are hard wired in the instrument cluster. When the park or head lamps are turned on, the cluster illumination lamps light.

Illumination brightness is adjusted by rotating the headlamp switch knob (clockwise to dim, counterclockwise to brighten). The instrument cluster illumination lamps receive battery feed from the panel dimmer rheostat in the headlamp switch through a fuse in the fuseblock module.

The instrument cluster electronic circuitry also monitors the cluster illumination lamp dimming level whenever the park or head lamps are turned on. The instrument cluster electronic circuitry responds by adjusting the dimming level of the odometer Vacuum Fluorescent Display (VFD), and sending dimming level messages over the Chrysler Collision Detection (CCD) data bus network. When the park lamps or headlamps are turned off, the VFD is illuminated at full brightness for improved daylight visibility.

Each of the cluster illumination lamps is located on the instrument cluster circuit board. Each cluster illumination lamp has a replaceable bulb and bulb holder.

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