Principles of Operation

PRINCIPLES OF OPERATION

The instrument cluster is a hybrid electronic instrument cluster (HEC). The instrument cluster gauges, warning indicators, and message center displays are either controlled and driven directly through hardwired circuitry, or the information is requested and received through the standard corporate protocol (SCP). The instrument cluster has self-test diagnostics capabilities using the diagnostic tool.

Instrument Cluster Gauges

Speedometer Gauge
The instrument cluster receives the vehicle speed signal from the powertrain control module (PCM) over the communication network and displays it on the speedometer gauge. When the instrument cluster has no vehicle speed signal, the speedometer defaults to 0.0 km/h (0.0 mph).

Odometer
The instrument cluster receives odometer rolling count status from the PCM over the communication network and stores the mileage in non-volatile memory (NVM). Dashes are displayed in the odometer display and the ABS warning indicator is illuminated if the instrument cluster fails to receive the odometer rolling count status.

Fuel Gauge
The instrument cluster receives the fuel level information directly from the fuel sending unit. When the fuel level is low, the resistance is low. When the fuel level is high, the resistance is high.

Engine Coolant Temperature Gauge
Engine coolant temperature information is received by the instrument cluster from the powertrain control module (PCM) over the SCP communication network. Temperatures over 123°C (253°F) will cause the engine coolant temperature gauge to display hot (H). If the engine coolant temperature data is missing or invalid, the instrument cluster will move the engine coolant temperature gauge to the cold (C) position.

Integrated Circuit Displays
The instrument cluster has 2 vacuum fluorescent, fixed format, integrated circuit displays. The integrated circuit displays will prove out by fully illuminating all segments for several seconds when the ignition switch is first turned on. The instrument cluster message center switch is used to scroll through the display functions of the trip computer. The instrument cluster message center switch is comprised of two buttons, SELECT and RESET.

In addition to the trip computer functions, the low washer (WASHER) fluid is displayed in the RH integrated circuit display.

Instrument Cluster Message Center SELECT Button
The RH integrated circuit display SELECT button functions are as follows:
- redundant digital speed
- average and instant fuel economy
- fuel remaining
- distance to empty (DTE)
- average speed
- trip A/B
- English/Metric

Instrument Cluster Message Center RESET Button
The RH integrated circuit display RESET button will control the following functions:
- redundant digital speed
- fuel economy
- trip A
- trip B
- English/Metric
- average speed

The LH integrated circuit display indicates:
- AIR SUSPENSION
- CHECK FUEL CAP
- DOOR AJAR
- odometer
- CHECK GAUGE
- TRUNK AJAR
- O/D OFF
- SPEED CONTROL
- redundant digital speed display

Indicators

O/D OFF
The overdrive off (O/D OFF) display illuminates depending on the overdrive telltale command the instrument cluster receives from the PCM over the communication network. If the O/D switch is depressed, turning the overdrive off, the O/D OFF illuminates.

CHECK FUEL CAP
The CHECK FUEL CAP display is used to indicate significant leaks in the evaporative emissions system due to a loose, missing or defective fuel cap, or other fuel evaporative concern. The fuel tank pressure is monitored by the PCM. If a leak is detected, the PCM signals a fault to the instrument cluster through the communication network. Once the PCM has detected a major leak and the CHECK FUEL CAP indicator is illuminated, the CHECK FUEL CAP indicator will remain illuminated until the fuel cap has been secured and the vehicle has been operated for several minutes.

SPEED CONTROL
The SPEED CONTROL display illuminates when the instrument cluster receives an ON vehicle speed control high resolution set speed command from the PCM through the communication network. The speed control servo receives its input directly from the speed control switch. If the instrument cluster fails to receive a vehicle speed high resolution set speed command, the instrument cluster defaults to the last known value. After each ignition cycle, if no command is received, the instrument cluster defaults and does not illuminate the SPEED CONTROL display.

AIR SUSPENSION
The AIR SUSPENSION display illuminates depending on the suspension system state status message the instrument cluster receives from the air suspension control module over the communication network. If the instrument cluster fails to receive a suspension system state status after the 3 second prove-out duration, the instrument cluster continues to illuminate the AIR SUSPENSION display. The instrument cluster will only turn off the AIR SUSPENSION display if it receives a suspension system state status message with no failure indicated.

Vehicle Speed Display
The vehicle speed display is a redundant speed indication and operates in conjunction with the speedometer. The instrument cluster receives the vehicle speed data for both the redundant display and the speedometer from the PCM over the communication network.

DOOR AJAR
The DOOR AJAR display illuminates when any of the doors (LF, RF, LR, or RR) are open or ajar. The instrument cluster receives the door ajar data from the lighting control module (LCM) over the communication network.

TRUNK AJAR
The TRUNK AJAR display illuminates when the trunk is open or ajar. The instrument cluster receives the trunk ajar data from the LCM through the communication network.

Low Oil Pressure Warning Indicator
The low oil pressure warning indicator receives the oil pressure status directly from the oil pressure switch. With the ignition switch in the ON position, the low oil pressure warning indicator illuminates. After the engine is started and the oil pressure builds up, the oil pressure switch opens and turns off the low oil pressure warning indicator.

Warning Indicators

BRAKE System Warning Indicator
The BRAKE system warning indicator proves out when the ignition switch is in the START position, grounding the circuit. The indicator illuminates if the brake fluid level is low or if the parking brake pedal is depressed.

Safety Belt Warning Indicator
The safety belt warning indicator illuminates if the driver or passenger safety belts are fastened when the ignition switch is turned to the ON position. The instrument cluster receives the safety belt status from the LCM. The safety belt warning indicator turns off after 60 seconds from when the engine was started, regardless of the driver or passenger safety belt status. An audible safety belt chime is provided by the LCM if the instrument cluster detects the driver safety belt to be unfastened.

CHECK GAUGE Warning Indicator
The instrument cluster carries out a 3-second prove-out of the check gauge warning indicator when the ignition switch is in the ON position. After the engine is started, the PCM sends the instrument cluster a fail-safe cooling mode status. If the instrument cluster does not receive a message from the PCM, the instrument cluster assumes the OFF status and turns off the indicator.

SERVICE ENGINE SOON Indicator
The SERVICE ENGINE SOON indicator is illuminated with the ignition switch in the ON position. After the engine is started, the SERVICE ENGINE SOON indicator remains on for a prove-out duration of 3 seconds. If the PCM fails to send the instrument cluster an OFF status message, the SERVICE ENGINE SOON indicator remains illuminated. After the prove-out duration, the SERVICE ENGINE SOON indicator is controlled directly by the PCM over the communication network to the instrument cluster.

Traction Control Indicator
The traction control indicator receives its data from the ABS module through the communication network. The traction control indicator display illuminates if the traction control is active. Once the vehicle enters into a skid condition, the instrument cluster receives a traction control active telltale command message over the communication network from the ABS module.

High Beam Indicator
The high beam indicator is controlled by the LCM over the communication network. When the headlamps are turned on, the LCM sends the instrument cluster a high beam indicator telltale command ON message. The instrument cluster does not prove out the high beam indicator. If the instrument cluster does not receive a high beam indicator telltale command from the LCM, the instrument cluster does not illuminate the high beam indicator.

Air Bag Warning Indicator
The air bag warning indicator is controlled by the restraint control module (RCM). The instrument cluster receives the air bag data through hardwired circuitry to the RCM.

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 goes out after the engine is started and the charging system begins to operate. The instrument cluster receives the charging system warning indicator ground signal from the PCM through hardwired circuitry. 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.

ABS Warning Indicator
The ABS warning indicator has multiple functions. The instrument cluster proves out the ABS warning indicator when the ignition switch is turned to the ON position. After the engine is started, the instrument cluster monitors the messages for the odometer rolling count status from the PCM. If at any time the instrument cluster does not receive this message every 2 seconds, the instrument cluster illuminates the ABS indicator.

Left and Right Turn Signal Indicators
The left and right turn signal indicators on the instrument cluster are controlled by the multifunction switch and also operate together when the hazard lamps are turned on.

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