Principles of Operation

PRINCIPLES OF OPERATION

The instrument cluster contains an analog speedometer, tachometer, fuel gauge, engine coolant temperature gauge, oil pressure gauge and battery voltage gauge. The instrument cluster receives the information through hardwired circuitry. Each time the ignition switch is turned from the OFF to the ON position the instrument cluster proves out the indicators. The charging system warning indicator, and the CHECK ENGINE warning indicator stay illuminated until the engine is started and operating normally. The safety belt warning indicator proves out for 60 seconds or until the driver safety belt is buckled. The following instrument cluster indicators proves out as follows:
- air bag (6 seconds)
- anti-lock brake system (ABS) (3 seconds)
- brake (3 seconds)
- low fuel (2 seconds)
- air suspension (2 seconds)
- fail-safe cooling (3 seconds)
- electronic throttle control (ETC) (3 seconds)
- traction control (3 seconds)

Engine Coolant Temperature Gauge
The engine coolant temperature gauge indicates the engine coolant temperature based on the operating resistance range from the engine coolant temperature sender. If the engine coolant temperature is low, the sender resistance is high. If the engine coolant temperature is high, the sender resistance is low. The engine coolant temperature sender resistance range should be between 9.7 ohms and 74 ohms.

Oil Pressure Gauge
The oil pressure gauge indicates the engine oil pressure status. The instrument cluster is hardwired to the normally open oil pressure switch. With the engine running, the oil pressure switch closes and provides a ground to the instrument cluster and moves the oil pressure gauge pointer into the normal range. When oil pressure is low or the engine is not running, the oil pressure switch opens and removes the ground to the instrument cluster moving the oil pressure gauge pointer into the low range.

Voltage Gauge
The voltage gauge displays the system voltage as measured at the instrument cluster run input.

Fuel Gauge
The fuel gauge receives the fuel level resistance from the fuel level sensor, part of the fuel pump module. To prevent the fuel gauge pointer from fluctuating as a result of excessive movement of fuel in the fuel tank, the fuel indicator module provides a delay to the fuel gauge. If the fuel level is low, the resistance in the fuel level sensor will be low, causing the gauge to indicate empty (E). When the fuel level is high, the resistance in the fuel level sensor is high, and the gauge indicates full (F). The fuel indicator module also turns on the low fuel indicator when the fuel gauge shows approximately one-eighth of a tank of fuel remaining or less.

Speedometer/Odometer
The speedometer and odometer provides speed and distance information based on a speed/distance signal from the powertrain control module (PCM). The PCM receives the vehicle speed information from the output shaft speed sensor (OSS).

Warning Indicators

Air Bag Warning Indicator
The air bag warning indicator is controlled by the restraint control module (RCM). When starting the vehicle, the air bag warning indicator illuminates and remains lit for 6 seconds. The indicator only illuminates after starting the vehicle if a supplemental restraint system malfunction is detected.

Anti-Lock Brakes Warning Indicator
The anti-lock brake system (ABS) warning indicator illuminates when the ABS module detects a fault in the system.

Brake System Warning Indicator
The brake system warning indicator has a dual function. It illuminates when the parking brake is applied or when a low brake fluid condition exists in the brake master cylinder reservoir. The brake system warning indicator illuminates when there is a pressure differential between the front and rear brake hydraulic systems.

Charging System Warning Indicator
The charging system warning indicator illuminates whenever the generator output is insufficient to maintain battery state of charge or if the generator output is too high. Under normal operation, the indicator turns off after the engine is started and the charging system begins to operate. The charging system warning indicator is hardwired to the PCM. When the charging system output is low, the PCM provides a ground path to the instrument cluster and turns on the charging system warning indicator.

Fail-Safe Cooling Warning Indicator
The fail-safe cooling system allows limited engine operation in the event of excessive engine temperature. The fail-safe cooling mode is entered when engine temperature exceeds approximately 124°C (255°F) as measured by the cylinder head temperature (CHT) sensor.

During fail-safe cooling mode:
- the engine coolant temperature gauge moves to hot (H).
- the thermometer symbol illuminates.
- the CHECK ENGINE warning indicator illuminates.
- the PCM disables 4 of the 8 cylinders by turning their respective fuel injectors off. This reduced performance allows the engine to cool down.

When the engine temperature reaches approximately 166°C (330°F) the:
- engine coolant temperature gauge remains pointed to hot (H).
- thermometer symbol flashes.
- CHECK ENGINE warning indicator remains illuminated.
- PCM disables all eight cylinders by turning their respective fuel injectors off, resulting in engine shut down.

Low Fuel Warning Indicator
The low fuel warning indicator is controlled by the fuel indicator module and warns the driver when the fuel level is one-eighth or lower in the tank.

Overdrive Off Indicator
The overdrive off (O/D OFF) indicator has dual functions. The O/D OFF indicator illuminates when the overdrive is turned off. The O/D OFF indicator also illuminates if a fault is detected in the automatic transmission.

Safety Belt Warning Indicator
The safety belt indicator is directly hardwired to the lighting control module (LCM). The LCM controls the safety belt indicator depending on the signal it receives from the safety belt buckle switch. The safety belt warning indicator illuminates when the safety belt is not buckled, closing the safety belt buckle switch.

Check Fuel Cap Indicator
The CHECK FUEL CAP indicator is used to indicate significant leaks in the fuel tank evaporative system due to a loose fuel cap. The instrument cluster is hardwired to the PCM. Fuel tank pressure is monitored by the PCM and if a leak is detected, it signals a fault to the instrument cluster and provides a ground to illuminate the CHECK FUEL CAP indicator. Once the PCM has detected a loose fuel cap and the CHECK FUEL CAP indicator is illuminated, the indicator will remain illuminated until the fuel cap is secured and the vehicle has been running for several minutes or the ignition has been cycled once.

Electronic Throttle Control (ETC) Warning Indicator
The ETC warning indicator is hardwired to the PCM. The PCM controls the warning indicator and illuminates the warning indicator when a system concern is detected.

CHECK ENGINE Warning Indicator
The CHECK ENGINE warning indicator is hardwired to the PCM. The PCM controls the malfunction indicator lamp (MIL) and illuminates when a diagnostic trouble code (DTC) is detected.

Traction Control Indicator
The traction control indicator flashes when the vehicle traction control is in active mode or is being controlled by the anti-lock brake system (ABS) module. The traction control indicator is hardwired to the ABS module and illuminates when the ABS module detects a concern.