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Part 1





OPERATION

INDICATORS

Indicators are located in various positions within the Instrument Panel Cluster (IPC), and are all connected to the electronic circuit board, and are completely controlled by the IPC microprocessor. The various indicators are controlled by different strategies; some receive fused ignition switch output from the IPC circuitry and have a switched ground, while others are grounded through the circuitry and have a switched battery feed. However, most are controlled by Controller Area Network (CAN) data bus messages from other electronic modules in the vehicle, but some are controlled by a combination of hard-wired inputs, electronic messaging, and IPC programming. If the IPC loses CAN data bus communication, the internal circuitry of the IPC will automatically turn ON the Malfunction Indicator Lamp (MIL) until CAN data bus communication is restored.

Certain indicators in the IPC are automatically or self-configured. This feature allows the configurable indicators to be enabled by the IPC circuitry for compatibility with certain optional equipment. These indicators are enabled or disabled by an electronic configuration message sent to the IPC by the Body Control Module (BCM). The automatically or self-configured indicators remain latent in each BCM at all times and will be active only when the IPC receives the appropriate CAN bus message inputs for that optional system or equipment.

Below are brief explanations of the indicators available on this vehicle. More detailed information may be available elsewhere under the module or system sections that control or influence the illumination of an indicator located within the instrument cluster or the Vacuum Florescent Display (VFD). The indicators, the VFD display as well as the gauges are only serviceable with the instrument cluster as an assembly. The cluster lens and hood assembly are the only components serviceable separate of the instrument cluster.

ANTILOCK BRAKE SYSTEM (ABS) INDICATOR

The ABS indicator gives an indication to the vehicle operator when the ABS system is faulty or inoperative. This indicator is controlled by the IPC circuit board based upon programming and electronic messages received from the Controller Antilock Brake (CAB) over the CAN data bus. The IPC will illuminate the ABS indicator for about three seconds each time the ignition is turned to the ON position, during the bulb test.

The ABS indicator is completely controlled by the IPC logic circuit, and only allows this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED will always be off when the ignition switch is in any position except ON or START. The indicator only illuminates when it is provided a path to ground by the IPC transistor. The IPC will also illuminate the ABS indicator for the following reasons:

- ABS Lamp-ON Message - Each time the IPC receives a lamp-on message from the CAB, the ABS indicator will be illuminated. The indicator remains illuminated until the IPC receives a lamp-off message from the BCM, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Communication Error - If the IPC receives no lamp-on or lamp-off messages from the CAB for five consecutive message cycles, the ABS indicator is illuminated. The indicator remains illuminated until a valid message from the CAB is received, or until the ignition switch is turned to the OFF position, whichever occurs first.
- ABS Diagnostic Test - The ABS indicator is blinked on and off by lamp-on and lamp-off messages from the CAB during the performance of the ABS diagnostic tests.

The CAB continually monitors the ABS circuits and sensors to decide whether the system is in good operating condition. The CAB then sends the proper lamp-on or lamp-off messages to the IPC. If the CAB sends a lamp-on message after the bulb test, it indicates that the CAB has detected a system malfunction and/or that the ABS system has become inoperative. The CAB will store a Diagnostic Trouble Code (DTC) for any malfunction it detects. Each time the ABS indicator fails to light due to an open or short in the cluster ABS indicator circuit, the cluster sends a message notifying the CAB of the condition, then the instrument cluster and the CAB will each store a DTC.

AIRBAG INDICATOR

The airbag indicator gives an indication to the vehicle operator when the airbag system is faulty or inoperative. The airbag indicator is controlled by the IPC circuit board based upon programming and electronic messages received from the Occupant Restraint Controller (ORC) over the CAN data bus. Based on messages received from the ORC, the IPC will illuminate the airbag indicator for about six seconds each time the ignition is turned to the ON position, during the bulb test.

The airbag indicator LED is completely controlled by the IPC logic circuit, and only allows this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED will always be off when the ignition switch is in any position except ON or START. The LED only illuminates when it is provided a path to ground by the IPC transistor. The IPC will also illuminate the airbag indicator for the following reasons:

- ORC Lamp-ON Message - Each time the IPC receives a lamp-on message from the ORC, the airbag indicator will be illuminated. The indicator remains illuminated for about twelve seconds or until a lamp-off message from the ORC is received, whichever is longer.
- Communication Error - If the IPC receives no airbag messages for ten consecutive message cycles, the airbag indicator is illuminated. The indicator remains illuminated until the IPC receives a single lamp-off message from the ORC.

The ORC continually monitors the airbag system circuits and sensors to decide whether the system is in good operating condition. The ORC then sends the proper lamp-on or lamp-off messages to the IPC. If the ORC sends a lamp-on message after the bulb test, it indicates that the ORC has detected a system malfunction and/or that the airbags and seat belt tensioners may not deploy when required, or may deploy when not required. The ORC will store a DTC for any malfunction it detects. Each time the airbag indicator fails to illuminate due to an open or short in the IPC airbag indicator circuit, the IPC sends a message notifying the ORC of the condition, the IPC and the ORC will each store a DTC, and the seat belt indicator will flash on and off as a backup to notify the vehicle operator.

BRAKE/PARK BRAKE INDICATOR

The brake indicator gives an indication to the vehicle operator when the parking brake is applied, when there are certain brake hydraulic system malfunctions as indicated by a low brake hydraulic fluid level condition, or when the brake fluid level switch is disconnected. The brake indicator can also give an indication when certain faults are detected in the ABS. This indicator is controlled by a transistor on the IPC circuit board based upon programming, electronic messages received from the CAB over the CAN data bus, and a hard-wired input from the park brake switch. The IPC will illuminate the brake indicator for about three seconds each time the ignition is turned to the ON position, during the bulb test.

The brake indicator LED is completely controlled by the IPC logic circuit, and only allows this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LED will always be off when the ignition switch is in any position except ON or START. The LED only illuminates when it is provided a path to ground by the IPC transistor. The IPC will also illuminate the brake indicator for the following reasons:

- Brake Lamp-ON Message - Each time the IPC receives a lamp-on message from the CAB, the brake indicator will be illuminated. The CAB can also send brake lamp-on messages as feedback during ABS diagnostic procedures. The indicator remains illuminated until the a lamp-off message from the CAB is received, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Park Brake Switch Input - Each time the IPC detects ground on the park brake switch sense circuit (park brake switch closed = park brake applied or not fully released) while the ignition switch is in the ON position, and vehicle speed in 8km (4.9 mph) or greater, the brake indicator flashes on and off. The indicator continues to flash until the park brake switch sense input to the IPC is an open circuit (park brake switch open = park brake fully released), or until the ignition switch is turned to the OFF position, whichever occurs first.

The park brake switch on the park brake pedal mechanism provides a hard-wired ground input to the IPC circuitry through the park brake switch sense circuit whenever the park brake is applied or not fully released. The CAB continually monitors the ABS system circuits and sensors, including the brake fluid level switch on the brake master cylinder reservoir, to decide whether the system is in good operating condition. The CAB then sends the proper lamp-on or lamp-off messages to the IPC. If the CAB sends a lamp-on message after the bulb test, it indicates that the CAB has detected a brake hydraulic system malfunction and/or that the ABS system has become inoperative. The CAB will store a DTC for any malfunction it detects.
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