Part 4

OPERATION

TRACTION CONTROL INDICATOR

The traction control indicator gives an indication to the vehicle operator when the Electronic Stability Program (ESP)/Brake Assist System (BAS)/Traction Control System (TCS) has been activated. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received by the cluster from the Controller Antilock Brake (CAB) over the Controller Area Network (CAN) data bus. Each time the ignition switch is turned to the ON position the traction control indicator is illuminated for about four seconds as a bulb test. The entire bulb test is a function of the CAB.

The traction control indicator 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 provided a path to ground by the instrument cluster circuitry. The instrument cluster will turn ON the traction control indicator for the following reasons:

- Traction Control Indicator Lamp-On Message - Each time the cluster receives an electronic traction control indicator lamp-ON message from the CAB indicating that the ESP/BAS/TCS has been activated, the traction control indicator will be illuminated. The indicator can be flashed ON and OFF, or illuminated solid, as dictated by the CAB message. The indicator remains illuminated solid or continues to flash until the cluster receives a lamp-OFF message from the CAB, or until the ignition switch is turned to the OFF position, whichever occurs first.

The CAB continually monitors the traction control switch to determine the proper outputs to the components of the Antilock Brake System (ABS). The CAB then sends the proper lamp-ON or lamp-OFF message to the ElectroMechanical Instrument Cluster (CCN) (also known as the Cab Compartment Node/CCN).

TRANSMISSION RANGE INDICATOR

The electronic gear selector indicator gives an indication to the vehicle operator of the transmission gear that has been selected with the automatic transmission gear selector lever. This indicator is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received from the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus.

The gear selector indicator information is displayed by the odometer Vacuum Fluorescent Display (VFD) unit soldered onto the instrument cluster electronic circuit board, and the VFD will not display the gear selector indicator information after the ignition switch is turned to the OFF position. Each time the cluster is disconnected from battery current for more than about five minutes, it must configure itself for the automatic transmission type that is in the vehicle once it is reconnected to battery current. The instrument cluster circuitry operates the gear selector indicator to provide the following features:

- Selected Gear Message - Each time the cluster receives an electronic selected gear message from the PCM, a box will be illuminated around the appropriate character in the gear selector indicator. The box will remain illuminated until the cluster receives a different selected gear message, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Communication Error - If the cluster fails to receive a selected gear message from the PCM within three seconds, the instrument cluster circuitry will display all gear selector positions boxed (selected) until a valid selected gear message is received or until the ignition switch is turned to the OFF position, whichever occurs first.

The PCM continually monitors a hard-wired multiplex input from the Transmission Range Sensor (TRS), then sends the proper message to the ElectroMechanical Instrument Cluster (CCN) (also known as the Cab Compartment Node/CCN).

TRANSMISSION TEMPERATURE INDICATOR

The transmission over-temperature indicator gives an indication to the vehicle operator when the transmission fluid temperature is excessive, which may lead to accelerated transmission component wear or failure. 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 Controller Area Network (CAN) data bus. Each time the ignition switch is turned to the ON position the transmission over temperature indicator is illuminated for about two seconds as a bulb test.

The transmission over-temperature indicator Light Emitting Diode (LED) 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 LED is always 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 turns on the transmission over-temperature indicator for the following reasons:

- Trans Over-Temp Indicator Lamp-On Message - Each time the cluster receives an electronic transmission over temp indicator lamp-on message from the PCM indicating that the transmission fluid temperature is 135 °C (275 °F) or higher, the indicator illuminates and a single chime tone is sounded. The indicator remains 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 only repeats during the same ignition cycle if the indicator is cycled off and then on again by the appropriate lamp-on and lamp-off messages from the PCM.

The PCM continually monitors the transmission temperature sensor to determine the transmission operating condition. The PCM then sends the proper lamp-on or lamp-off message to the instrument cluster, also known as the Cab Compartment Node (CCN). If the instrument cluster illuminates the transmission over temperature indicator due to a high transmission oil temperature condition, it may indicate that the transmission or the transmission cooling system are being overloaded, or that they require service. For further diagnosis of the transmission over-temperature indicator or the instrument cluster circuitry that controls the LED, Testing and Inspection.

TURN SIGNAL INDICATORS

The turn signal indicators give an indication to the vehicle operator that the turn signal (left or right indicator flashing) or hazard warning (both left and right indicators flashing) have been selected and are operating. These indicators are controlled by transistors on the instrument cluster electronic circuit board based upon the cluster programming and electronic messages received from the Totally Integrated Power Module (TIPM) over the Controller Area Network (CAN) data bus.

Each turn signal indicator Light Emitting Diode (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, each 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 turn signal indicators for the following reasons:

- Turn Signal Indicator Lamp-On Message - Each time the cluster receives an electronic right or left turn signal-ON message from the TIPM over the CAN data bus, the appropriate turn signal indicator will be flashed ON and OFF. The TIPM also sends the appropriate electronic message to the cluster to control the flash rate of the turn signal indicators, as well as to control the click rate of an electromechanical relay soldered onto the cluster electronic circuit board that emulates the sound emitted by a conventional turn signal flasher. The turn signal indicators continue to flash ON and OFF until the cluster receives a lamp-OFF message from the TIPM, or until the ignition switch is turned to the OFF position, whichever occurs first.
- Hazard Warning Indicator Lamp-On Message - Each time the cluster receives an electronic hazard warning-ON message from the TIPM over the CAN data bus, both turn signal indicators will be flashed ON and OFF. The TIPM also sends the appropriate electronic messages to the cluster to control the flash rate of the right and left turn signal indicators, as well as to control the click rate of an electromechanical relay soldered onto the cluster electronic circuit board that emulates the sound emitted by a conventional hazard warning flasher. The turn signal indicators continue to flash ON and OFF until the cluster receives a hazard warning-OFF message from the TIPM.
- Turn Signal-On Textual Warning Message - When the cluster detects that a turn signal has been active continuously for 1.6 kilometers (1 mile) with the vehicle speed greater than 22 kilometers-per-hour (15 miles-per hour) a chime tone will be sounded and, if the vehicle is so equipped, a TURN SIGNAL ON textual message will appear within the instrument cluster reconfigurable Vacuum Fluorescent Display (VFD) unit.
- Lamp Out Mode - If the TIPM detects an ineffective turn signal lamp or circuit, it increases the flash rate for the remaining operative turn signals and sends an electronic message to the instrument cluster. To provide an indication of the problem to the vehicle operator the instrument cluster then increases the flash rate of the turn signal indicators, the click rate of the electromechanical relay and, if the vehicle is so equipped, displays a TURN SIGNAL LAMP OUT textual message in the reconfigurable VFD unit.

The ElectroMechanical Instrument Cluster (CCN) (also known as the Cab Compartment Node/CCN) continually monitors the electronic messages from the TIPM to determine the proper turn signal and hazard warning indicator operation.