Part 3

OPERATION

GAS CAP INDICATOR

The gas cap indicator gives an indication to the vehicle operator when there is a gross leak detected in the on-board fuel vapor recovery system. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received over the CAN data bus from the PCM.

The gas cap indicator function of the LCD display unit is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LCD gas cap indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the gas cap indicator for the following reasons:

- Gas Cap Indicator Lamp-On Message - Each time the cluster receives an electronic gas cap indicator lamp-ON message from the PCM indicating there is a gross leak in the vapor recovery system, the gas cap indicator will be displayed. The indicator remains displayed until the cluster receives a lamp-OFF message from the PCM, until the cluster arbitrator logic determines that another display request has priority, or until the ignition switch is turned to the OFF position, whichever occurs first.

The PCM continually monitors the on board vapor recovery system to determine whether there are air leaks in the system. The PCM then sends the proper lamp-ON or lamp-OFF message to the CCN. If the CCN turns ON the gas cap indicator due to a monitored gross leak in the vapor recovery system, it may indicate that the gas cap has been removed or is improperly installed.

For proper diagnosis of the on board vapor recovery system, the PCM, the CCN, the CAN data bus or the electronic communication related to gas cap indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

HIGH BEAM INDICATOR

The high beam indicator gives an indication to the vehicle operator whenever the headlamp high beams are illuminated. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received from the Front Control Module (FCM) over the CAN data bus.

The high beam indicator LED is completely controlled by the instrument cluster logic circuit, and that logic will allow this indicator to operate whenever the instrument cluster receives a battery current input on the fused B(+) circuit. Therefore, the LED can be illuminated regardless of the ignition switch position. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the high beam indicator for the following reasons:

- High Beam Indicator Lamp-On Message - Each time the cluster receives an electronic high beam indicator lamp-ON message from the FCM the high beam indicator will be illuminated. The high beam indicator remains illuminated until the cluster receives a lamp-OFF message from the FCM, or until the exterior lamp load shedding (battery saver) timed interval expires, whichever occurs first.

The FCM continually monitors electronic messages from the CCN and the SmartBeam(R) module on vehicles so equipped to determine the proper headlamp beam control. The FCM activates or deactivates the headlamp high beams then sends the proper lamp-ON or lamp-OFF message back to the CCN.

For proper diagnosis of the SmartBeam(R) module, the FCM, the CCN, the CAN data bus or the electronic communication related to high beam indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

HILL DESCENT INDICATOR

The hill descent indicator gives an indication to the vehicle operator when the QuadraDrive four-wheel drive transfer case gear selector is in the 4WD LOW position and the hill descent control push button in the instrument panel switch pod has been depressed to turn the feature ON. This feature uses the grade sensing logic of the CAB to sense the vehicle is descending a hill and employs the brake system to automatically control the hill descent speed of the vehicle. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received over the CAN data bus from the CAB.

The hill descent indicator function of the LCD display unit is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LCD hill descent indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the hill descent indicator for the following reasons:

- Hill Descent Indicator Lamp-On Message - Each time the cluster receives an electronic hill descent indicator lamp-ON message from the CAB, the indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the CAB, until the cluster arbitrator logic determines that another display request has priority, or until the ignition switch is turned to the OFF position, whichever occurs first.

The CAB continually monitors electronic message inputs from the Final Drive Control Module (FDCM) and the CCN to determine the status of the QuadraDrive four-wheel drive system and the hill descent control switch, then monitors its own internal grade sensing logic to determine when the hill descent mode should be engaged. The CAB then sends the proper lamp-ON or lamp-OFF message to the CCN.

For proper diagnosis of the hill descent control switch, the FDCM, the CAB, the CCN, the CAN data bus or the electronic communication related to hill descent indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

LIFTGATE AJAR INDICATOR

The power liftgate indicator gives an indication to the vehicle operator of the system status or when the system has been automatically disabled. This indicator is controlled by the CCN logic circuit based upon programming and electronic messages received over the CAN data bus from the Power LiftGate Module (PLGM).

The power liftgate indicator function of the LCD display unit is completely controlled by the instrument cluster logic circuit, and that logic will allow this indicator to operate whenever the instrument cluster receives a battery current input on the fused B(+) circuit. Therefore, the LCD power liftgate indications can be illuminated regardless of the ignition switch position. The instrument cluster will turn ON the power liftgate indicator for the following reasons:

- Unlock To Operate Message - Each time the CCN receives an electronic unlock to operate message from the PLGM, the UNLOCK TO OPERATE textual message is displayed. The message is displayed for about three seconds or until the cluster arbitrator logic determines that another display request has priority, whichever occurs first.
- Put In Park To Operate Message - Each time the CCN receives an electronic put in PARK to operate message from the PLGM, the PUT IN PARK TO OPERATE textual message is displayed. The message is displayed for about three seconds or until the cluster arbitrator logic determines that another display request has priority, whichever occurs first.
- Function Disabled Message - Each time the CCN receives an electronic function disabled message from the PLGM, the FUNCTION DISABLED textual message is displayed. The message is displayed for about three seconds or until the cluster arbitrator logic determines that another display request has priority, whichever occurs first.
- Close Liftgate Glass Message - Each time the CCN receives an electronic close liftgate glass message from the PLGM, the CLOSE LIFTGLASS textual message is displayed. The message is displayed for about three seconds or until the cluster arbitrator logic determines that another display request has priority, whichever occurs first.
- Obstacle Detected Message - Each time the CCN receives an electronic obstacle detected message from the PLGM, the OBSTACLE DETECTED textual message is displayed. The message is displayed for about three seconds or until the cluster arbitrator logic determines that another display request has priority, whichever occurs first.
- Manually Close To Operate Message - Each time the CCN receives an electronic manually close to operate message from the PLGM, the MANUAL CLOSE TO OPERATE textual message is displayed. The message is displayed for about three seconds or until the cluster arbitrator logic determines that another display request has priority, whichever occurs first.

The PLGM continually monitors the power liftgate inputs to determine the proper outputs to the power liftgate components. The PLGM then sends the proper lamp-ON or lamp-OFF message to the CCN.

For proper diagnosis of the power liftgate, the PLGM, the CCN, the CAN data bus or the electronic communication related to power liftgate indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

LOW COOLANT INDICATOR

The coolant low indicator gives an indication to the vehicle operator when the diesel engine coolant level is low. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received over the CAN data bus from the PCM.

The coolant low indicator function of the LCD display unit is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the LCD coolant low indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the coolant low indicator for the following reasons:

- Coolant Low Indicator Lamp-On Message - Each time the cluster receives an electronic coolant low indicator lamp-ON message from the PCM indicating the engine coolant level is low, the coolant low textual warning and icon are illuminated and a single chime tone is sounded. The coolant low textual warning and icon remain illuminated until the cluster receives a lamp-OFF message from the PCM, or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the textual warning and icon are cycled OFF and then ON again by the appropriate messages from the PCM.

The PCM continually monitors the engine coolant level switch on the coolant bottle to determine the level of the engine coolant. The PCM then sends the proper lamp-ON or lamp-OFF message to the CCN. If the instrument cluster turns ON the coolant low indicator and icon due to a low coolant level, it may indicate that the engine or the engine cooling system requires service.

For proper diagnosis of the engine coolant level switch, the PCM, the CCN, the CAN data bus or the electronic communication related to coolant low indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

LOW FUEL INDICATOR

The low fuel indicator gives an indication to the vehicle operator when the level of fuel in the fuel tank becomes low. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and a hard-wired input received by the cluster from the fuel level sending unit on the fuel pump module in the fuel tank. The CCN will illuminate the low fuel indicator for about three seconds each time the ignition is turned to the ON position, during the bulb test.

The low fuel indicator LED is completely controlled by the instrument cluster logic circuit, and that logic will only allow 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 instrument cluster transistor. The instrument cluster will turn ON the low fuel indicator for the following reasons:

- Less Than 11 Percent Tank Full Input - The cluster provides a constant current source to the fuel level sending unit and monitors a return input on a fuel level sense circuit. The resistance through the fuel level sending unit increases as the fuel level falls and decreases as the fuel level rises causing changes in the sense input voltage. Each time the fuel level sense input to the cluster indicates the fuel tank is about 11 percent full or less for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, the gauge needle is moved to the appropriate position on the gauge scale, the low fuel indicator is illuminated, and a single chime tone is sounded. The low fuel indicator remains illuminated until the fuel level sense input indicates that the fuel tank is greater than about 14 percent full for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the low fuel indicator is cycled OFF and then ON again by the appropriate inputs from the fuel level sending unit.
- Less Than Empty Stop Input - Each time the cluster receives a fuel level sense input that indicates the fuel level in the fuel tank is less than the E (or Empty) gauge needle stop position for five consecutive seconds, the gauge needle is moved to the low end of the gauge scale and the low fuel indicator is illuminated immediately. This input would indicate that the fuel level sense input to the cluster is a short circuit.
- More Than Full Stop Input - Each time the cluster receives a fuel level sense input that indicates the fuel level in the fuel tank is more than the F (or Full) gauge needle stop position for five consecutive seconds, the gauge needle is moved to the low end of the gauge scale and the low fuel indicator is illuminated immediately. This input would indicate that the fuel level sense input to the cluster is an open circuit.

The CCN continually monitors the fuel tank sending unit to determine the level of fuel in the fuel tank. The cluster then sends the proper electronic fuel level message to other electronic modules in the vehicle over the CAN data bus. The cluster will store a DTC for any fault detected in the fuel level sense circuit.

For proper diagnosis of the fuel tank sending unit, the CCN, the CAN data bus or the electronic communication related to low fuel indicator operation or fuel level data processing a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

LOW OIL PRESSURE INDICATOR

The low oil pressure indicator gives an indication to the vehicle operator when the engine oil pressure reading reflects 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 PCM over the CAN data bus.

The low oil pressure indicator LED is completely controlled by the instrument cluster logic circuit, and that logic will only allow 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 instrument cluster transistor. The instrument cluster will turn ON the low oil pressure indicator for the following reasons:

- Engine Oil Pressure Low Message - Each time the cluster receives an electronic engine oil pressure message from the PCM indicating the pressure is about 6.9 kPa (1 psi) or lower, the low oil pressure indicator will be illuminated. The indicator can be flashed ON and OFF, or illuminated solid, as dictated by the PCM message. The indicator remains illuminated solid or flashing until the cluster receives a message from the PCM indicating that the pressure is above about 6.9 kPa (1 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 low engine oil pressure if the engine speed is greater than zero.

The PCM continually monitors the engine oil pressure sensor to determine the engine oil pressure. The PCM then sends the proper messages to the CCN. If the CCN turns ON the indicator after the bulb test, it may indicate that the engine or the engine oiling system requires service.

For proper diagnosis of the engine oil pressure sensor, the PCM, the CCN, the CAN data bus or the electronic communication related to low oil pressure indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

LOW TIRE PRESSURE INDICATOR

The Tire Pressure Monitor (TPM) indicator gives an indication to the vehicle operator of the status of the TPM system. 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 Wireless Ignition Node (WIN) over the CAN data bus. The CCN will illuminate the TPM indicator for about three seconds each time the ignition is turned to the ON position, during the bulb test

The TPM indicator LED is completely controlled by the instrument cluster logic circuit, and that logic will only allow 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 provide a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the TPM indicator for the following reasons:

- TPM Indicator Lamp-On Message - Each time the cluster receives an electronic TPM indicator lamp-ON message from the WIN, the TPM indicator or the TIRE LOW PRESSURE textual message will be illuminated. The indicator can be flashed ON and OFF, or illuminated solid, as dictated by the WIN message. The indicator or textual message remains illuminated until the cluster receives a lamp-OFF message from the WIN, or until the ignition switch is turned to the OFF position, whichever occurs first.
- TPM Textual Warning Message - When the WIN detects certain monitored fault conditions, it will send electronic messages requesting the cluster display a textual warning message. Each time the cluster receives an electronic textual warning request message from the WIN, a SERVICE TIRE PRESS. SYSTEM textual message will appear within the cluster re-configurable dot matrix display to accompany a flashing TPM indicator or to replace the TPM TIRE LOW PRESSURE textual message. This message indicates that the WIN has detected a problem in one of the TPM system components.
- TPM Low Pressure Message - On vehicles equipped with the optional premium version of the TPM system, each time the cluster receives an electronic low pressure message from the WIN, a LEFT FRONT, RIGHT FRONT, LEFT REAR or RIGHT REAR LOW PRESSURE textual message will appear within the cluster re-configurable dot matrix display to accompany a solid TPM indicator. If the vehicle is equipped with a full-sized matching spare tire and wheel assembly, an electronic spare low pressure message from the WIN to the cluster will cause a SPARE LOW PRESSURE textual message will appear in the re-configurable display, but the TPM indicator will not illuminate. This message indicates that the WIN has received a low tire pressure input from the tire pressure sensor in the identified location on the vehicle. The premium TPM system is not offered in markets where rear fog lamps are an available option.
- Communication Error - If the cluster receives no TPM lamp-ON or lamp-OFF messages from the WIN for six consecutive seconds, the TPM indicator is illuminated by the instrument cluster. The indicator remains controlled and illuminated by the cluster until a valid lamp-ON or lamp-OFF message is received from the WIN.

The WIN performs a self-test each time the ignition switch is turned to the ON position to decide whether the TPM system is in good operating condition and whether the tire inflation pressures are too high or too low. The WIN then sends the proper lamp-ON or lamp-OFF message to the CCN. If the instrument cluster turns ON the TPM indicator after the bulb test, it indicates that the inflation pressure of a tire is too low or that a malfunction has occurred and the TPM system is ineffective.

For proper diagnosis of the TPM system, the WIN, the CCN, the CAN data bus or the electronic communication related to TPM indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.