The turn signal switch is integrated into the steering column module. When the turn signal switch is activated, the steering column module interprets the position of the switch and sends a serial data message to the underhood electrical center (UEC) and the rear electrical center (REC) requesting either the right or left turn signals be activated. The UEC and REC respond by applying a pulsating voltage to the appropriate turn signal control circuits to illuminate the front and rear turn signal lamps. The steering column module also sends a serial data message to the instrument panel cluster (IPC) requesting the appropriate turn signal indicator be illuminated.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool Turn Signal Status parameter while cycling the turn signal switch between the left and right positions. The parameter should change between Inactive, Right F1, Right F2, Left F1, and Left F2.

⇒	If the parameter does not change between the commanded states, replace the steering column module.

⇒	If the parameter changes between the commanded states and the turn signal indicators are inoperative, refer to Turn Signal Indicators Malfunction.

2. Command the front turn signals ON and OFF with a scan tool. The front turn signal lamps should illuminate ON and OFF when changing between the commanded states.

⇒	If the front turn signals do not illuminate when commanded, refer to Front Turn Signal Lamps Malfunction.

3. Command the rear turn signals ON and OFF with a scan tool. The rear turn signal lamps should illuminate ON and OFF when changing between the commanded states.

⇒	If the rear turn signals do not illuminate when commanded, refer to Rear Turn Signal Lamps Malfunction.

4. Command the Side Repeater Test ON and OFF with a scan tool. The side repeater lamps should illuminate ON and OFF when changing between the commanded states.

⇒	If the side repeater lamps do not illuminate when commanded, refer to Repeater Lamps Malfunction.

Front Turn Signal Lamps Malfunction

1. Ignition OFF, disconnect the harness connector at the inoperative front turn signal lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal 1 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 5 and ground.
4. Command the Front Turn Signal Test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the UEC.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the UEC.

5. If all circuits test normal, replace the inoperative front turn signal lamp.

Rear Turn Signal Lamps Malfunction

1. Ignition OFF, disconnect the harness connector at the inoperative rear tail lamp assembly.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.

•	Left rear tail lamp ground terminal 1 - 3 Door

•	Left rear tail lamp ground terminal 6 - 5 Door

•	Right rear tail lamp ground terminal 6 - 3 Door

•	Right rear tail lamp ground terminal 1 - 5 Door

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.

•	Left rear turn signal lamp control terminal 6 - 3 Door

•	Left rear turn signal lamp control terminal 4 - 5 Door

•	Right rear turn signal lamp control terminal 1 - 3 Door

•	Right rear turn signal lamp control terminal 3 - 5 Door

4. Command the rear turn signals ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the REC.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the REC.

5. If all circuits test normal, replace the inoperative tail lamp circuit board.

Repeater Lamps Malfunction

1. Ignition OFF, disconnect the harness connector at the inoperative repeater lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal 2 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 1 and ground.
4. Command the Side Repeater Test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the UEC.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the UEC.

5. If all circuits test normal, replace the inoperative repeater lamp.

Turn Signal Indicators Malfunction

Ignition ON, with a scan tool perform the Turn Signal Telltale Test for the instrument panel cluster (IPC) and observe the left and right turn signal indicators.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.