Part 3 of 8

BRAKE/PARK BRAKE INDICATOR
A brake indicator is standard equipment on all instrument clusters. The brake indicator is located in the Information Center area of the instrument cluster; to the right of center. The brake indicator consists of a stenciled cutout of the word "BRAKE" and the International Control and Display Symbol icons for "Brake Failure" and "Parking Brake" in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. A red lens behind the cutout in the opaque layer of the overlay causes the "BRAKE" text and the two icons to appear in red through the translucent outer layer of the overlay when the indicator is illuminated from behind by a Light Emitting Diode (LED) soldered onto the instrument cluster electronic circuit board. The brake indicator is serviced as a unit with the instrument cluster.

The brake indicator gives an indication to the vehicle operator when the parking brake is applied, or when there are certain brake hydraulic system malfunctions. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming, and electronic messages received by the cluster from the Central Timer Module (CTM) and the Controller Antilock Brake (CAB) over the Programmable Communications Interface (PCI) data bus. The brake indicator Light Emitting Diode (LED) receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions; 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 instrument cluster transistor. The instrument cluster will turn ON the brake indicator for the following reasons:

- Bulb Test - Each time the ignition switch is turned to the ON position the brake indicator is illuminated by the instrument cluster for about four seconds as a bulb test.

- Brake Lamp-ON Message - Each time the cluster receives a lamp-ON message from the CTM or the CAB, the brake indicator will be illuminated. If the park brake is applied or not fully released, or if the pressures in the two halves of the split brake hydraulic system are not equal with the ignition switch in the ON position, the brake indicator is illuminated solid. The brake indicator will blink ON and OFF repeatedly when the park brake is applied or not fully released and the ignition switch is in the ON position if the automatic transmission is not in Park or Neutral. The indicator remains illuminated until the cluster receives lamp-off messages from both the CTM and the CAB, or until the ignition switch is turned to the OFF position, whichever occurs first.

- Actuator Test - Each time the instrument cluster is put through the actuator test, the brake indicator will be turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.

The park brake switch on the park brake pedal mechanism provides a hard wired ground input to the CTM circuitry through the park brake switch sense circuit whenever the park brake is applied or not fully released. The CTM then sends the proper lamp-ON or lamp-OFF messages to the instrument cluster. The brake pressure switch on the brake combination valve provides a hard wired ground input to the CAB circuitry through the brake pressure switch sense circuit whenever the pressures in the two halves of the split brake hydraulic system are unequal. The CAB then sends the proper lamp-ON or lamp-OFF messages to the instrument cluster. 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 Diagnostic Trouble Code (DTC) for any malfunction it detects. The park brake switch input to the CTM and the brake pressure switch input to the CAB can be diagnosed using conventional diagnostic tools and methods. For proper diagnosis of the antilock brake system, the CTM, the CAB, the PCI data bus, or the message inputs to the instrument cluster that control the brake indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.

CHECK GAUGES INDICATOR
A check gauges indicator is standard equipment on all instrument clusters. The check gauges indicator is located in the Information Center area of the instrument cluster, to the right of center. The check gauges indicator consists of a stenciled cutout of the words "CHECK GAGES" in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. A red lens behind the cutout in the opaque layer of the overlay causes the "CHECK GAGES" text to appear in red through the translucent outer layer of the overlay when the indicator is illuminated from behind by a Light Emitting Diode (LED) soldered onto the instrument cluster electronic circuit board. The check gauges indicator is serviced as a unit with the instrument cluster.

The check gauges indicator gives an indication to the vehicle operator when certain instrument cluster gauge readings reflect a condition requiring immediate attention. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The check gauges indicator Light Emitting Diode (LED) receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions; 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 instrument cluster transistor. The instrument cluster will turn ON the check gauges indicator for the following reasons:

- Bulb Test - Each time the ignition switch is turned to the ON position the check gauges indicator is illuminated for about two seconds as a bulb test.

- Engine Temperature High Message - Each time the cluster receives a message from the PCM indicating the engine coolant temperature is about 122 °C (253 °F) or higher, the check gauges indicator will be illuminated. The indicator remains illuminated until the cluster receives a message from the PCM indicating that the temperature is about 119 °C (246 °F) or lower, or until the ignition switch is turned to the OFF position, whichever occurs first.

- Engine Oil Pressure Low Message - Each time the cluster receives a message from the PCM indicating the engine oil pressure is about 3.45 kPa (0.5 psi) or lower, the check gauges indicator will be illuminated. The indicator remains illuminated until the cluster receives a message from the PCM indicating that the engine oil pressure is above 3.45 kPa (0.5 psi), or until the ignition switch is turned to the OFF position, whichever occurs first. The cluster will only turn the indicator ON in response to an engine oil pressure low message if the engine speed is greater than zero.

- System Voltage Low Message - Each time the cluster receives a message from the PCM indicating the electrical system voltage is less than 11.5 volts, the check gauges indicator will be illuminated. The indicator remains illuminated until the cluster receives a message from the PCM indicating the electrical system voltage is greater than 12.0 volts (but less than 16.6 volts), or until the ignition switch is turned to the OFF position, whichever occurs first.

- System Voltage High Message - Each time the cluster receives a message from the PCM indicating the electrical system voltage is greater than 16.6 volts, the check gauges indicator will be illuminated. The indicator remains illuminated until the cluster receives a message from the PCM indicating the electrical system voltage is less than 16.1 volts (but greater than 11.5 volts), or until the ignition switch is turned to the OFF position, whichever occurs first.

- Actuator Test - Each time the cluster is put through the actuator test, the indicator will be turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the LED and the cluster control circuitry.

The PCM continually monitors the engine temperature, oil pressure, and electrical system voltage, then sends the proper messages to the instrument cluster. For further diagnosis of the check gauges indicator or the instrument cluster circuitry that controls the LED, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the check gauges indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.

CRUISE INDICATOR
A cruise indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with the optional speed control system, this indicator is electronically disabled. The cruise indicator consists of the word "CRUISE", which appears in the lower portion of the odometer/trip odometer Vacuum-Fluorescent Display (VFD). The VFD is part of the cluster electronic circuit board, and is visible through a cutout located in the lower left corner of the cluster overlay. The dark lens of the VFD prevents the indicator from being clearly visible when it is not illuminated. The word "CRUISE" appears in an amber color and at the same lighting level as the odometer/trip odometer information when it is illuminated by the instrument cluster electronic circuit board. The cruise indicator is serviced as a unit with the VFD in the instrument cluster.

The cruise indicator gives an indication to the vehicle operator when the speed control system is turned ON, regardless of whether the speed control is engaged. This indicator is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus. The cruise indicator receives battery current ON the instrument cluster electronic circuit board through the fused ignition switch output (run- start) circuit whenever the ignition switch is in the ON or Start positions; therefore, the indicator will always be OFF when the ignition switch is in any position except ON or Start. The indicator only illuminates when it is switched to ground by the instrument cluster circuitry. The instrument cluster will turn ON the cruise indicator for the following reasons:

- Bulb Test - Each time the ignition switch is turned to the ON position the cruise indicator is illuminated for about two seconds as a bulb test.

- Cruise Lamp-ON Message - Each time the cluster receives a cruise lamp-ON message from the PCM indicating the speed control system has been turned ON, the cruise indicator is illuminated. The indicator remains illuminated until the cluster receives a cruise lamp-OFF message from the PCM or until the ignition switch is turned to the OFF position, whichever occurs first.

- Actuator Test - Each time the cluster is put through the actuator test, the cruise indicator will be turned ON, then OFF again during the VFD portion of the test to confirm the functionality of the VFD, and again during the bulb check portion of the test to confirm the functionality of the cluster control circuitry.

The PCM continually monitors the speed control switches to determine the proper outputs to the speed control servo. The PCM then sends the proper cruise indicator lamp-on and lamp-OFF messages to the instrument cluster. For further diagnosis of the cruise indicator or the instrument cluster circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the speed control system, the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the cruise indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.