The tachometer is an analog gauge located in the instrument panel gauge (IPC). The tachometer is operated by the IPC under the 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 located in the IPC. The temperature gauge is operated by the IPC under the 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 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 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 to appropriately display the engine oil pressure. A sensor resistance of 1ohms will display as 0 PSI (0 kPa) and a resistance of 88ohms will display as 80 PSI (80 kPa). The IPC also monitors the oil pressure sensor circuit and interprets the current flow in this circuit. The IPC decides when the engine oil pressure is too low. The check gauges tell tale should be turned ON. The oil pressure sender is located on the left side of the 2.2L engine. 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 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. When the ignition switch is turned to any other position, the pointer may rest at any position. 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 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 the resistance is low. The VCM/PCM interprets this signal and sends a 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 generally 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 a float attached to the following components:

For the 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 will have 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. In some fuel tank senders, a short connector lead is used while others have the connector attach directly to the sender.

The speedometer is an analog gauge located in the IPC. The speedometer is operated by the IPC under 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 leads to a malfunctioning instrument cluster. 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 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 to the tire size of each vehicle. If the final drive or the tire size is changed for any reason, you must update the PCM/VCM to match the new final drive or the tire size. If you do not update the PCM/VCM, the signal will be inaccurate for proper speedometer/odometer operation. An incorrect signal can affect antilock brakes and 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 two-wheel drive models. The VSS mount to the transfer case output shaft housing on 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 the START position. The voltmeter indicates nominal electrical system voltage. When the engine is running, the indicator should be between 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 the 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 the contents.

The purpose of illuminating the IPC LED and the telltale displays on power up is to verify that the segments of the LED telltale displays are working. The turn signal indicators do not turn ON during this test. Do not attempt further diagnosis unless all of the segments appear leading to misdiagnosis. If any portions or segments of the IPC displays are inoperative, you must first diagnose the IPC. Refer to Instrument Cluster System Check.