Turn Signal Lamps

NOTE:

The turn signal switch is integral to the left multi-function switch of the SCCM. The SCCM also includes a microcontroller, which communicates with the BCM/CBC over the CAN data bus. Before performing any of the following tests, determine whether the other functions of the left multi-function switch are operational. If the other left multi-function switch are ineffective, diagnose and repair that problem before attempting to repair the Turn Signal Lamps.

Turn Lamp Fault Environment - Diagnoses is performed for the front and rear turns signal lamps by the BCM. If Combined Front Park/Turn is present on the vehicle, the BCM will only perform diagnostics when the turn signal is placed into an active state. If a left or right turn signal is requested and a faulted condition is present for either the front or rear turn signals at the time of the activation, the frequency of the CAN-B signals will show doubled corresponding to the side of the fault. If the left or right side has a faulted condition, the cluster will send an internal signal to display to the driver the faulted condition. However, the BCM output frequency to the lamps will not be changed during this faulted state. Even if the CAN-B frequency is doubled, the output from the BCM to the lamps will still be driven at a normal operating frequency.

It is required that, during the same ignition cycle, if a turn signal lamp or bulb is replaced, the system will recover with no intervention by the technician. Starting the vehicle and disconnecting a turn signal bulb or LED will result in an open fault. Replacing the bulb or LED lamp assembly causes the fault to change from active to stored. Normal signaling behavior will returns. This process applies to any of the six exterior lighting turn signal displays in use for this vehicle.

CONDITION	POSSIBLE CAUSES	CORRECTION
ONE TURN SIGNAL LAMP DOES NOT ILLUMINATE	1. Ineffective or missing bulb.	1. Test and replace turn signal bulb if required.
	2. Ineffective ground circuit.	2. Test and repair open ground circuit if required.
	3. Ineffective feed circuit.	3. Test and repair open right or left turn signal feed circuit if required.
	4. Ineffective BCM inputs or outputs.	4. Use a diagnostic scan tool to test the BCM inputs and outputs. Refer to the appropriate diagnostic information.
ALL RIGHT SIDE OR ALL LEFT SIDE TURN SIGNAL LAMPS (OR BOTH SIDES) DO NOT FLASH	1. Ineffective feed circuit.	1. Test and repair open right or left turn signal feed circuit if required.
	2. Ineffective EMIC (CCN) inputs or outputs.	2. Use a diagnostic scan tool and the appropriate diagnostic information for further EMIC diagnosis.
	3. Ineffective BCM inputs or outputs.	3. Use a diagnostic scan tool to test the BCM inputs and outputs. Refer to the appropriate diagnostic information.
ALL RIGHT SIDE OR ALL LEFT SIDE TURN SIGNALS DO NOT FLASH	1. Ineffective or missing bulb.	1. Test and replace turn signal bulb if required.
	2. Ineffective ground circuit.	2. Test and repair open bulb ground circuit if required.
	3. Ineffective feed circuit.	3. Test and repair open right or left turn signal feed circuit if required.
TURN SIGNALS DO NOT AUTOMATICALLY CANCEL	1. Ineffective cancel cam.	1. Inspect and replace the turn signal cancel cam (clockspring) if required.
	2. Ineffective cancel actuator.	2. Inspect and replace the turn signal cancel actuator (left multi-function switch) if required.