Principles of Operation

PRINCIPLES OF OPERATION

Speedometer/Odometer
The instrument cluster receives vehicle speed information from the powertrain control module (PCM) over the communication network. On vehicles equipped with gasoline engines, the PCM receives its signal from the output shaft speed sensor (OSS). On vehicles equipped with diesel engines, the PCM receives its signal from the vehicle speed sensor (VSS).

The SELECT/RESET button has 3 functions. First, pressing the SELECT/RESET button toggles between the odometer and trip odometer settings. When the trip odometer is displayed, pressing and holding the SELECT/RESET button will reset the trip odometer. There are 2 trip odometers available: A and B. Pressing the SELECT/RESET button while in trip odometer will toggle between trip odometer A and trip odometer B. Lastly, the instrument cluster self-test is entered by pressing and holding the SELECT/RESET button down with the ignition switch in the OFF position, then turning the ignition switch to RUN.

The instrument cluster receives odometer rolling count status from the PCM and stores the mileage in non-volatile memory (NVM). When the instrument cluster fails to receive the odometer rolling count status for more than 5 seconds, the odometer display shows dashes.

Tachometer
The instrument cluster receives tachometer information from the PCM over the communication network.

Fuel Gauge and Low Fuel Warning Indicator
The fuel level sender is hardwired to the instrument cluster. The instrument cluster sends a voltage signal to the fuel level sender, which contains a variable resistor. The instrument cluster uses the return voltage to determine fuel level. When the fuel gauge reads approximately 1/16th tank, the instrument cluster illuminates the low fuel warning indicator.

Battery Voltage Meter and Charging System Warning Indicator
The instrument cluster measures system voltage and indicates whether the electrical system is operating at normal voltages. When the system voltage is too high, or too low, the PCM sends a message over the communication network to the instrument cluster to illuminate the charging system warning indicator.

Oil Pressure Gauge
The instrument cluster sends a signal voltage to the normally open oil pressure switch. When oil pressure is detected, the switch closes, grounding the circuit and causing the oil pressure gauge to display normal oil pressure.

Engine Coolant Temperature Gauge
The instrument cluster receives information on the engine coolant temperature from the PCM over the communication network. When the engine coolant temperature is within normal operating range, the gauge needle will be in the normal range.

Safety Belt Warning Indicator
The driver safety belt switch is hardwired to the instrument cluster. When the safety belt is engaged, the driver safety belt switch grounds the circuit, causing the lamp to turn off. When the safety belt is unbuckled, the ground is removed and the instrument cluster illuminates the safety belt warning indicator, when required.

Brake Warning Indicator
The brake warning indicator receives its signals from:
- the parking brake switch which provides a ground when the parking brake is engaged.

- NOTE: The brake fluid level switch is part of the master cylinder and is not serviced separately.

the brake fluid level switch which provides a ground when the brake fluid level is low or an open circuit if the brake fluid level switch is disconnected.

- the anti-lock brake system (ABS) module when the ABS module detects a base brake system concern

Anti-Lock Brake System (ABS) Warning Indicator
The instrument cluster receives status information from the ABS module through a hardwired circuit from the ABS module. During normal operation, the ABS module supplies a ground to the ABS warning LED circuit, shutting the LED off. If the ABS module detects a fault, or if the ABS module is disconnected, ground is removed from the circuit, causing the ABS warning indicator to illuminate.

Air Bag Warning Indicator
The air bag warning indicator circuit is grounded by the restraint control module (RCM), through a hardwired circuit, when the RCM detects a fault in the air bag system. In addition, the RCM connector contains a shorting bar that grounds the circuit when the connector is disconnected. Failure of the air bag warning indicator to prove out once the ignition switch is turned to the RUN position indicates a fault in the air bag system.

Malfunction Indicator Lamp (MIL)
When there is a fault in the engine control system, the PCM sends a message over the communication network to the instrument cluster, to illuminate the MIL.

Check Fuel Cap Warning Indicator (if equipped)
When the PCM detects that there is a leak in the evaporative emissions (EVAP) system that could be the result of a loose fuel filler cap, the PCM sends a message over the communication network to the instrument cluster, illuminating the check fuel cap warning indicator.

High Beam Indicator
The high beam indicator illuminates when the multifunction switch is in the high beam position and sends a voltage signal to the instrument cluster.

Right and Left Turn Indicator
The right and left turn indicators illuminate when the multifunction switch is in either turn signal position (or the hazard lamps position) and sends a voltage signal to the instrument cluster.

Door Ajar Warning Indicator
The door ajar indicator illuminates when any of the vehicle doors are open.

Wait to Start Indicator (diesel only)
The PCM provides the ground for the wait to start indicator. The glow plugs and the wait to start indicator operate at the same time. The indicator illuminates until the PCM has provided time for the glow plugs to heat the combustion chamber. The PCM then sends a message over the communication network to the instrument cluster to turn off the indicator.

Water-in-Fuel Indicator (diesel only)
The PCM receives a ground signal when water is sensed in the fuel. The PCM sends a message over the communication network to the instrument cluster, to illuminate the water-in-fuel indicator.

Check Gauge Warning Indicator
The check gauge warning indicator illuminates when a low oil pressure or an engine over temperature condition exists.

Electronic Throttle Control (ETC) Indicator
The PCM monitors the ETC system and provides the instrument cluster with the ETC status over the communication network. When a system concern is detected, the PCM provides the instrument cluster with a signal commanding the instrument cluster to turn the ETC indicator on.