Part 3

OPERATION

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/ECM 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/ECM 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/ECM message. The indicator remains illuminated solid or flashing until the cluster receives a message from the PCM/ECM 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/ECM continually monitors the engine oil pressure sensor to determine the engine oil pressure. The PCM/ECM then sends the proper messages to the EMIC. If the EMIC turns ON the indicator after the bulb test, it may indicate that the engine or the engine oiling system requires service.

LOW TIRE PRESSURE

The Tire Pressure Monitor (TPM) indicator gives an indication to the vehicle operator of the status of the TPM system. The TPM 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 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 provided a path to ground by the instrument cluster transistor. Each time the ignition switch is turned to the ON position, the WIN sends an electronic TPM indicator lamp-ON message to the cluster to illuminate the TPM indicator for about three seconds as a bulb test. 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 indicator will be illuminated. The indicator can be flashed ON and OFF, or illuminated solid, as dictated by the WIN message. The indicator 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.
- 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 EMIC. 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 inoperative.

MALFUNCTION INDICATOR

The Malfunction Indicator Lamp (MIL) gives an indication to the vehicle operator when the PCM/ECM has recorded a DTC for an On-Board Diagnostics II (OBDII) emissions-related circuit or component malfunction. The MIL is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the PCM/ECM over the CAN data bus.

The MIL 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 indicator will always be OFF when the ignition switch is in any position except ON or START. The indicator only illuminates when it is energized by the instrument cluster logic circuit. Each time the ignition switch is turned to the ON position the indicator is illuminated for about 15 seconds as a bulb test. The entire bulb test is a function of the PCM/ECM. The instrument cluster will turn ON the MIL for the following reasons:

- MIL Lamp-On Message - Each time the cluster receives an electronic MIL lamp-ON message from the PCM/ECM, the indicator will be illuminated. The indicator can be flashed ON and OFF, or illuminated solid, as dictated by the PCM/ECM message. For some DTCs, if a problem does not recur, the PCM/ECM will send a lamp-OFF message automatically. Other DTCs may require that a fault be repaired and the PCM/ECM be reset before a lamp-OFF message will be sent. For more information on the PCM/ECM, and the DTC set and reset parameters, see EMISSIONS.
- Communication Error - If the cluster receives no lamp-ON or lamp-OFF messages from the PCM/ECM for 10 consecutive message cycles, the MIL is illuminated by the instrument cluster to indicate a loss of bus communication. The indicator remains controlled and illuminated by the cluster until a valid message is received from the PCM/ECM.

The PCM/ECM continually monitors the fuel and emissions system circuits and sensors to decide whether the system is in good operating condition. The PCM/ECM then sends the proper lamp-ON or lamp-OFF message to the EMIC. If the EMIC turns ON the MIL after the bulb test, it may indicate that a malfunction has occurred and that the fuel and emissions systems require service.

NO BUS INDICATOR

The no-bus indicator gives an indication to the vehicle operator when the electronic communication data bus is ineffective. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages not being received over the CAN data bus from the Front Control Module (FCM).

The no-bus indicator function of the odometer VFD unit is completely controlled by the instrument cluster logic circuit. This logic only allows the indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the odometer VFD no-bus indicator is always off when the ignition switch is in any position except ON or START. The instrument cluster turns ON the no bus indicator for the following reasons:

- No Electronic Communication Messages - Each time the ignition switch is turned to the ON position and the cluster does not receive electronic communication messages over the CAN data bus, the no-bus indicator illuminates. The indicator remains illuminated until CAN bus communication is restored or until the ignition switch turns to the OFF position, whichever occurs first.

The EMIC continually monitors the CAN data bus to determine the status of many sensors and systems throughout the vehicle. If bus communication is interrupted, the EMIC cannot provide accurate displays and outputs.

NO FUSE INDICATOR

The no fuse indicator gives an indication to the vehicle operator when the Ignition Off Draw (IOD) fuse is ineffective or is not installed. 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 TIPM.

The no fuse indicator function of the odometer VFD 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 odometer VFD no fuse indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the no fuse indicator for the following reasons:

- No Fuse Indicator Lamp-On Message - Each time the ignition switch is turned to the ON position and the cluster does not receive battery voltage from the IOD fuse, a no fuse indicator lamp-ON indicator will be illuminated. The indicator remains illuminated for about three seconds, until the IOD fuse is installed, until the trip odometer reset switch button is depressed or until the ignition switch is turned to the OFF position, whichever occurs first.

The TIPM continually monitors the IOD circuit to determine the status of the IOD fuse. The TIPM then sends the proper lamp-ON or lamp-OFF message to the EMIC.

CHANGE OIL INDICATOR

The change oil indicator gives an indication to the vehicle operator when a duty-cycle algorithm contained within the software of the PCM/ECM determines that a recommended oil change interval has been attained. 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/ECM.

The change oil indicator function of the odometer or Electronic Vehicle Information Center (EVIC) VFD 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 odometer or EVIC VFD change oil indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the change oil indicator for the following reasons:

- Change Oil Indicator Lamp-On Message - Each time the ignition switch is turned to the ON position and the cluster receives an electronic change oil indicator lamp-ON message from the PCM/ECM indicating that a duty-cycle based recommended oil change interval has been attained, the change oil indicator will be illuminated for about three seconds, until the trip odometer reset switch button or an EVIC steering wheel switch button is depressed, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Change Oil Indicator Reset Procedure - Once an engine oil change has been completed, the PCM/ECM duty cycle counters can be reset using the following procedure. Turn the ignition switch to the ON position, but DO NOT start the engine. Slowly depress and release the accelerator pedal fully three times within ten seconds. Turn the ignition switch to the OFF position. If the change oil indicator illuminates the next time the engine is started, repeat this procedure.

The PCM/ECM continually monitors numerous sensor inputs to determine the duty-cycles to which the engine is being subjected. A pre-programmed algorithm within the PCM/ECM then determines when to send the proper lamp-ON or lamp-OFF message to the EMIC.

REAR FOG LAMP INDICATOR

The rear fog lamp indicator gives an indication to the vehicle operator whenever the rear fog lamps are illuminated. 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 TIPM over the CAN data bus.

The rear fog lamp 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 rear fog lamp indicator for the following reasons:

- Rear Fog Indicator Lamp-On Message - Each time the cluster receives an electronic rear fog indicator lamp-ON message from the TIPM indicating the rear fog lamps are turned ON, the rear fog lamp indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the TIPM, or until the exterior lamp load shedding (battery saver) timed interval expires, whichever occurs first.

The TIPM continually monitors electronic exterior lighting request messages from the EMIC to determine the appropriate outputs to the rear fog lamps. The TIPM activates or deactivates the rear fog lamps then sends the proper lamp-ON or lamp-OFF message back to the EMIC.