The tachometer is an analog gauge that is located in the instrument panel cluster (IPC). The tachometer is operated by the IPC with software control. The VCM/PCM sends Tach pulses to the IPC on a discrete circuit at the rate of 2 pulses per engine revolution with the engine running. The IPC will interpret the tach pulses in order to appropriately display the engine RPM on the tachometer.

The temperature gauge is an analog device that is located in the IPC. The temperature gauge is operated by the IPC with software control. The VCM/PCM uses Class 2 communications in order to inform the IPC of the engine coolant temperature. The IPC operates the Temperature Gauge to appropriately display the engine coolant temperature. The VCM/PCM determines the coolant temperature by measuring the current from a variable resistance sensor in the engine coolant jacket with the ignition switch in the RUN position. The sensor changes resistance with the coolant temperature. As the coolant temperature increases the resistance of the sensor decreases. The coolant temperature sensor (CTS) is located in the thermostat housing on the 2.2L engine. The CTS of the 4.3L engine is located on the left side of the cylinder head.

The oil pressure gauge is an analog device that is located in the IPC. The oil pressure gauge is operated directly by the oil pressure sensor circuit. As the engine oil pressure changes, the resistance of the sensor and the current flow in the oil pressure gauge changes. 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 1ohms will display as 0 kPa (0 PSI) and a resistance of 88 ohms will display as 80 kPa (80 PSI ). The IPC also monitors the oil pressure sensor circuit and interprets the current flow in this circuit in order to determine when the engine oil pressure is too low. If the oil pressure is too low, the check gauges tell tale will turn on. The oil pressure sender is located on the left side of the 2.2L. The 4.3L engine, oil pressure sender is located at the top left side, near the distributor/high voltage switch.

The fuel gauge is an analog device that is located in the IPC. The IPC software operates the fuel gauge by the use of Class 2 messages from the VCM/PCM. The fuel gauge indicates the quantity of fuel in the tank when the ignition switch is in the RUN position.

The pointer may rest in any position when the ignition switch is in one of the following positions:

The VCM/PCM measures the current from a variable resistor inside of the fuel tank. The variable resistor 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 IPC. The new message indicates 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, the resistance is low. The VCM/PCM interprets this signal and sends a Class 2 message to the IPC. 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 cause the indicator to rest below EMPTY. The fuel gauge sender assembly mounts to the top of the fuel tank and is retained by a cam-type locking ring. A seal is used between the fuel tank and the sender.

The fuel gauge sender assembly consists of the following components:

For fuel gauge sender replacement procedures, refer to Fuel Sender Assembly Replacement in Engine Controls 2.2L or Fuel Sender Assembly Replacement in Engine Controls 4.3L. For diagnostic information regarding the fuel gauge, refer to Fuel Gage Inaccurate or Inoperative . The fuel gauge sender has 2 or 3 hose connections. One hose is used for the fuel feed hose. The second hose connects to the vapor canister. The third hose is used for the fuel return line to the fuel tank. Some fuel tank senders use a short connector lead. Others have the connector attach directly to the sender.

The speedometer is an analog gauge that is located in the IPC. The speedometer is operated by the IPC with software control. The VCM/PCM sends vehicle speed pulses to the IPC on a discrete circuit. The PCM/VCM sends a Class 2 message to the IPC when the engine is running. The IPC will then interpret the speed pulses in order to appropriately display the vehicle speed on the speedometer. An electric speedometer drive is standard equipment on all models. Integrated circuits control the air core speedometer and the electric odometer. Lighting is provided by a removable bulb and socket assemblies which insert into the back of the instrument cluster.

The speedometer system consists of the following components:

The one-piece instrument cluster mounts in front of the driver in the instrument panel. Replace the instrument cluster if the diagnosis indicates that the instrument cluster is malfunctioning. Refer to Instrument Cluster Replacement . Repairs to the instrument cluster can only be performed by an authorized instrument cluster service center. The PCM/VCM converts the analog output form the vehicle speed sensor to a digital signal containing 6,400 pulses per kilometer (4,000 pulses per mile) for the instrument cluster. The PCM/VCM is matched to the final drive and tire size of each vehicle. If the final drive or the tire size is changed for any reason, update the PCM/VCM in order to match the new final drive or tire size. If the PCM/VCM is not updated, the signal will be inaccurate for correct speedometer/odometer operation. An incorrect signal can affect antilock brakes and cruise control systems. The VSS is a permanent magnet signal generator that spends an analog signal proportional to the propeller shaft speed to the PCM/VCM. The VSS mounts to the transmission tailshaft extension housing on a two-wheel drive models and the transfer case output shaft housing on the four-wheel drive models.

The voltmeter is an analog gauge located in the IPC. The voltmeter measures the battery voltage when the ignition switch is in the RUN or START position. The voltmeter indicates nominal electrical system voltage. When the engine is running, the indicator should be 10-16 volts. If the indicator is not within these limits with the engine running refer to Charging System Check in Engine Electrical. The voltmeter has a red band at each extreme end of its range. The indicator rests outside of either band normally. If the indicator rests inside either band a charging system problem is indicated.

The electronic odometer/tripometer is a variable function LED display located in the IPC. The electronic odometer/tripometer is configured to display miles or kilometers. The season display will increment to a maximum display of 999,999 units (miles or kilometers). The tripometer display will show a maximum of 9,999.9 units (miles or kilometers). The season display will not roll over to all zeros once the maximum is reached but will continue to display the maximum. The Tripometer display can be reset by holding the trip button depressed for 2 seconds. If the vehicle battery is disconnected, the tripometer will not retain its contents.

The purpose of illuminating the IPC LED and the telltale displays on power up is to verify the segments of the LED the telltale displays are working. The turn signal indicators do not turn ON during this check. Further diagnosis should not be attempted unless all of the segments appear leading to misdiagnosis. If any portions or segments of the IPC displays are inoperative, the IPC must be diagnosed first. Refer to Instrument Cluster System Check .