The gauges located in the instrument cluster provide the driver with vehicle information. Each gauge utilizes a specific viscosity (thickness) of damping fluid in order to ensure smooth and steady operation of the needle. The IPC controls gauge increments in each gauge by information received on the serial data line or by a dedicated circuit from other systems.

The temperature gauge is an analog device that is located in the instrument cluster. The VCM/PCM uses class 2 serial data communications in order to inform the instrument cluster of the engine coolant temperature. The instrument cluster operates the temperature gauge in order to appropriately display the engine coolant temperature. The VCM/PCM determines the coolant temperature by measuring current from a variable resistance sensor in the engine coolant jacket with the ignition switch in the RUN position. The sensor changes resistance with coolant temperature. As coolant temperature increases, the resistance of the sensor decreases. The coolant temperature gauge displays temperatures of 160°F, 210°F, and 260°F.

The electronic odometer/trip odometer is a display that is located in the instrument cluster. The electronic odometer/trip odometer is configured to display miles or kilometers. The odometer will increment to a maximum display of 999,999 miles or kilometers. The trip odometer will show a maximum of 9,999.9 miles or kilometers and then will roll over to all zeros. The odometer will not roll over to all zeros once the maximum is reached, but will continue to display the maximum miles or kilometers. The trip odometer display can be reset by holding the trip button depressed for 2 seconds.

The electronic shift indicator (PRNDL) is a class 2 serial data message to the instrument cluster from the PCM/VCM. The vacuum florescent (VF) display utilizes the fixed gear position labels P, R, N, D, 3, 2, 1 surrounded by a moveable square flag in order to indicate the selected gear position. Since the system is entirely electronic, there is no internal adjustment. The PRNDL display will operate as follows:

The fuel gauge is an analog device that is located in the instrument cluster. The instrument cluster operates the fuel gauge by the class 2 serial data messages from the VCM/PCM. The fuel gauge shows the quantity of fuel in the tank when the ignition switch is in the RUN position. When the ignition switch is turned to the OFF, LOCK, START, or ACC position, the pointer may come to rest at any position.

The VCM/PCM measures current from a variable resistor inside the fuel tank that is controlled by a float. When the fuel tank is full and the ignition switch is in the RUN position, the resistance signal to the VCM/PCM is high. The VCM/PCM interprets this signal and sends a message to the instrument cluster indicating the percentage of fuel in the tank over the class 2 serial data line. The fuel gauge indicator then moves to the maximum position or FULL on the gauge face. When the fuel tank is empty, resistance is low. The VCM/PCM interprets this signal and sends a class 2 serial data message to the instrument cluster. The fuel gauge indicator then moves to the minimum position or EMPTY on the gauge face. Corroded connections or severed ground paths generally cause the indicator to register past FULL on the gauge face. Short circuits to ground generally result in the indicator resting below EMPTY.

The instrument cluster has the capability to display accumulated engine run time hours using the vacuum florescent (VF) display when the cluster is in the LOCK or the ACC position. The hours will accumulate only with the ignition switch in the RUN position and the engine running. The cluster stores the accumulated hours so that if the battery was disconnected or removed the accumulated hours would not change. The cluster will display the accumulated hours when the ignition switch is in the OFF position and the trip reset stem is pushed in and held for more than four seconds. The accumulated hours will be displayed for 30 seconds and then turn OFF. The hourmeter will roll over to 0.0 when 10,000 hours are accumulated, and begin to accumulate hours again.

The oil pressure analog gauge in the instrument cluster is operated directly by the oil pressure sensor circuit with the ignition switch in RUN or START. As the engine oil pressure changes, the resistance of the sensor changes and the current flow in the oil pressure gauge causes the needle to move in order to appropriately display the engine oil pressure. A sensor resistance of 1 ohms will display as 0 PSI (0 kPa) and a resistance of 88 ohms will display as 80 PSI (550 kPa). The instrument cluster also monitors the oil pressure sensor circuit and interprets the current flow in this circuit in order to decide when engine oil pressure is too low and the Check Eng Oil Pressure message will be displayed in the message center.

The purpose of illuminating the instrument cluster PRNDL and indicator displays on power up is to verify that segments of the PRNDL and indicator displays are working. The turn signal indicators do not turn ON during this check. Further diagnosis should not be attempted unless all segments appear, as this could lead to misdiagnosis. If any portions or segments of the instrument cluster displays are inoperative, the instrument cluster must be diagnosed first.

The speedometer is an analog gauge in the instrument cluster. The VCM/PCM sends vehicle speed pulses to the instrument cluster on a designated circuit.

The speedometer system consists of the instrument cluster, vehicle speed sensor (VSS), PCM/VCM and related wiring. Repairs to the instrument cluster can only be performed by an authorized instrument cluster service center.

The PCM/VCM converts the analog output from the vehicle speed sensor to a digital signal containing 4,000 pulses per mile (PPM) for the instrument cluster. The PCM/VCM is matched to the final drive and tire size of each vehicle. If the final drive or tire size is changed for any reason, the PCM/VCM must be updated in order to match the new final drive or tire size. If not, the signal will not be accurate for proper speedometer/odometer operation. An incorrect signal can affect the antilock brakes and the cruise control systems.

The VSS is a permanent magnet signal generator that sends an analog signal proportional to the propeller shaft speed to the PCM/VCM. The VSS mounts to the transmission tailshaft extension housing on 2-wheel drive models and the transfer case output shaft housing on 4-wheel drive models.

The tachometer is an analog gauge in the instrument cluster. The VCM/PCM sends tach pulses to the instrument cluster on dedicated circuit at the rate of 2 pulses per engine revolution when the engine is running. The instrument cluster will then use the tach pulses to display engine RPM on the tachometer.

The transmission temperature gauge is an analog device in the instrument cluster. The VCM/PCM uses class 2 serial data communications in order to inform the instrument cluster of the transmission temperature. The instrument cluster operates the transmission temperature gauge in order to display the transmission temperature. The transmission temperature gauge displays temperatures of 100°F, 200°F, and 300°F.

The voltmeter is an analog gauge in the instrument cluster. The voltmeter measures battery voltage when the ignition switch is in the RUN or START positions. The voltmeter displays the electrical system voltage. When the engine is running, the indicator should be between 10 and 16 volts.

The voltmeter has a red band at each extreme end of its range. It is normal operation for the indicator to rest just outside of either band. If the indicator rests inside either band, a charging system problem is indicated.