Part 4

OPERATION- Continued

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 CCN circuit board based upon programming and electronic messages received 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 CCN transistor. The CCN will turn on the low oil pressure indicator for the following reasons:

- Engine Oil Pressure Low Message - Each time the CCN receives a message from the PCM indicating the engine oil pressure is about 4 psi (27.5 kPa) or lower, the low oil pressure indicator will be illuminated. The indicator remains illuminated until the CCN receives a message from the PCM indicating that the engine oil pressure is above about 4 psi (27.5 kPa), or until the ignition switch is turned to the OFF position, whichever occurs first. The CCN will only turn the indicator on in response to an engine oil pressure low message 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 engine oil pressure messages to the CCN.

LOW TIRE PRESSURE INDICATOR

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 the CCN circuit board based upon programming and electronic messages received from the Wireless Control Module (WCM) 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 is completely controlled by the CCN,s instrument cluster logic circuit, that logic only allow's this indicator to operate when the CCN 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 logic circuit. The CCN will illuminate the TPM indicator for the following reasons:

- TPM Indicator Lamp-ON Message - Each time the CCN receives an electronic TPM indicator lamp-ON message from the WCM, the indicator will be illuminated. The indicator can be flashed ON and OFF, or illuminated solid, as dictated by the WCM message. The indicator remains illuminated until the cluster receives a lamp-OFF message, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Low Tire Textual Message - ON vehicles manufactured for export markets, each time the CCN receives an electronic TPM indicator lamp-ON message from the WCM requesting the TPM indicator be illuminated solid, a LOtIRE textual message will appear within the odometer VFD display. The LOtIRE textual message remains displayed until the CCN receives a lamp-OFF message, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Communication Error - If the CCN receives no TPM lamp-ON or lamp-OFF messages from the WCM for six consecutive seconds, the TPM indicator is illuminated. The indicator remains controlled and illuminated by the CCN until a valid lamp-ON or lamp-OFF message is received from the WCM.

MALFUNCTION INDICATOR LAMP

The MIL gives an indication to the vehicle operator when the PCM has recorded a DTC for an ON-Board Diagnostics II (OBDII) emissions-related circuit or component malfunction. The MIL is controlled by a transistor on the CCN circuit board based upon programming and electronic messages received from the PCM over the CAN data bus. The CCN will illuminate the MIL indicator for about fifteen seconds each time the ignition is turned to the ON position, during the bulb test.

The MIL 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 CCN transistor. The CCN will also turn on the MIL for the following reasons:

- MIL Lamp-ON Message - Each time the CCN receives a MIL lamp-on message from the PCM, the indicator will be illuminated. The indicator can be flashed on and off, or illuminated solid, as dictated by the PCM message. For some DTC's, if a problem does not recur, the PCM will send a lamp-off message automatically. Other DTC's may require that a fault be repaired and the PCM be reset before a lamp-off message will be sent.
- Communication Error - If the CCN receives no messages from the PCM for ten consecutive message cycles, the MIL is illuminated by the CCN to indicate a loss of bus communication. The indicator remains illuminated until a valid message is received from the PCM.

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

OVERDRIVE OFF INDICATOR

The overdrive off indicator gives an indication to the vehicle operator when the electronically controlled overdrive feature of the automatic transmission has been disabled. This indicator is controlled by a transistor on the CCN circuit board based upon programming and electronic messages received from the PCM over the CAN data bus.

The overdrive off 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 CCN transistor. The CCN will illuminate the overdrive off indicator for the following reasons:

- Overdrive OFF Indicator Lamp-ON Message - Each time the CCN receives an electronic overdrive off indicator lamp-ON message from the PCM indicating that the overdrive-OFF position of the tow/haul switch has been selected, the indicator will be illuminated. The indicator remains illuminated until the CCN receives a lamp-OFF message from the PCM, or until the ignition switch is turned to the OFF position, whichever occurs first.

The PCM continually monitors the overdrive switch to determine the proper outputs to the automatic transmission. The PCM then sends the proper lamp-ON or lamp-OFF message to the CCN.

POSITION LAMP INDICATOR

The position lamp indicator gives an indication to the vehicle operator whenever the position lamps (exterior lighting) 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 position 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 position lamp indicator for the following reasons:

- Position Lamp Indicator Lamp-On Message - Each time the cluster receives an electronic position lamp indicator lamp-ON message from the TIPM indicating the position lamps are turned ON, the position 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 switch request messages from the CCN to determine the appropriate outputs to the park lamp relay. The TIPM activates or deactivates the park lamp relay then sends the proper lamp-ON or lamp-OFF message back to the CCN.