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 CCN electronic circuit board based upon the cluster programming, a hard wired multiplex input received by the cluster from the turn signal and hazard warning switch circuitry of the multi-function switch on the turn/hazard switch MUX circuit, and electronic messages received from the TIPM over the CAN data bus.

Each turn signal indicator LED is completely controlled by the CCN 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 CCN transistor. The CCN will turn on the turn signal indicators for the following reasons:

• Turn Signal-ON Input  - The Steering Control Module (SCM) sends a Data Bus message to the TIPM to turn on the turn signals. The TIPM also sends out a message to the CCN to illuminate the appropriate electronic turn signal switch indicator. The TIPM controls the output and the flash rate for either the right or left turn signal lamps and sends this message to the CCN. The CCN will then control the illumination and flash rate of the right or left turn signal indicators, as well as to control the click rate of an electromechanical relay soldered onto the CCN electronic circuit board that emulates the sound emitted by a conventional turn signal flasher. The turn signals and the turn signal indicators continue to flash on and off until the cluster receives a turn signal-off input from the multi-function switch, or until the ignition switch is turned to the OFF position, whichever occurs first.
• Hazard Warning-ON Input  - The turn signal flashers are also controlled by the TIPM. The SCM sends a Data Bus message to the TIPM and the TIPM responds to these messages by controlling a battery voltage output and the flash rate for each of the right and left turn signal lamps. The TIPM also sends the appropriate electronic messages back to the CCN to control the illumination and 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 CCN electronic circuit board that emulates the sound emitted by a conventional hazard warning flasher. The turn signals and the turn signal indicators continue to flash on and off until the cluster receives a hazard warning-off input from the multi-function switch.
• Lamp Out Mode  - The CCN also sends electronic turn signal on and off messages to the TIPM over the CAN data bus, and the TIPM flashes the appropriate exterior turn signal lamps. If the TIPM detects an inoperative turn signal lamp or circuit, it increases the flash rate for the remaining operative turn signals and sends an electronic message back to the instrument cluster. The instrument cluster then increases the flash rate of the turn signal indicator(s) and the clicking rate of the electromechanical relay to provide an indication of the problem to the vehicle operator.

The CCN continually monitors the multi-function switch and electronic messages from the TIPM to determine the proper turn signal and hazard warning system control.