Ground is applied at all times at G201 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM then applies a pulsating voltage to the front and rear turn signal lamps through their respective control circuits.

The tail lamp outage detection circuits are low current B+ circuits supplied by the BCM. For purposes of testing, a test lamp connected between the outage detection circuit and ground will not illuminate due to low current.

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 Right and Left Turn Signal Switch parameters while cycling the turn signal switch between the left and right positions. The parameters should change between Active and Inactive.

⇒	If the parameters do not change between the commanded states, refer to Turn Signal Switch Malfunction.

⇒	If the parameters change between the commanded states, refer to Turn Signal Lamps Malfunction.

2. Observe the right and left turn signal indicators while cycling the turn signal switch between the left and right positions. The turn signal indicators should illuminate when changing between the commanded states.

⇒	If the indicators do not change between the commanded states, refer to Turn Signal Indicators Malfunction.

3. Observe the left turn signal lamps and turn signal indicator on the IPC while activating the left turn signals. The left turn signal lamps and indicator should illuminate and flash when turned ON - uplevel only.

⇒	If the left turn signal lamps and indictor illuminate but flash in a rapid manner, refer to Tail Lamp Outage Detection Malfunction.

4. Observe the right turn signal lamps and turn signal indicator on the IPC while activating the right turn signals. The right turn signal lamps and indicator should illuminate and flash when turned ON - uplevel only.

⇒	If the left turn signal lamps and indictors illuminate but flash in a rapid manner, refer to Tail Lamp Outage Detection Malfunction.

Turn Signal Switch Malfunction

1. Ignition OFF, disconnect the X2 harness connector at the turn signal/multifunction switch.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

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

3. Ignition ON, verify the scan tool Left Turn Signal Switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal G for a short to ground. If the circuit tests normal, replace the BCM.

4. Verify the scan tool Right Turn Signal Switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal H for a short to ground. If the circuit tests normal, replace the BCM.

5. Install a 3A fused jumper wire between the signal circuit terminal G and ground. Verify the scan tool Left Turn Signal Switch parameter is Active.

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

6. Install a 3A fused jumper wire between the signal circuit terminal H and ground. Verify the scan tool Right Turn Signal Switch parameter is Active.

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

7. If all circuits test normal, test or replace the turn signal/multifunction switch.

Turn Signal Lamps Malfunction

1. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 1 ohm between the appropriate ground circuit terminal listed below and ground.

•	Left front repeater ground terminal B

•	Left front park/turn signal ground terminal G

•	Right front repeater ground terminal B

•	Right front park/turn signal ground terminal G

•	Left tail lamp ground terminal 3

•	Left stop/tail/turn signal ground terminal C

•	Right tail lamp ground terminal 3

•	Right stop/tail/turn signal ground terminal C

⇒	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 front repeater control terminal A

•	Left front park/turn signal control terminal A

•	Right front repeater control terminal A

•	Right front park/turn signal control terminal A

•	Left tail lamp control terminal 2

•	Left stop/tail/turn signal control terminal A

•	Right tail lamp control terminal 2

•	Right stop/tail/turn signal control terminal A

4. Command the appropriate Turn Signal Lamp 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 BCM.

⇒	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 BCM.

5. If all circuits test normal, replace the appropriate turn signal lamp assembly.

Tail Lamp Outage Detection Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate rear tail lamp assembly.
2. Ignition ON, test for B+ between the signal circuit terminal 1 and ground.

⇒	If the measured voltage is less than B+, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

3. Ignition ON, connect a test lamp between the signal circuit terminal 1 and ground. The test lamp should not Illuminate.

⇒	If the test lamp illuminates, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the tail lamp assembly.

Turn Signal Indicators Malfunction

Ignition ON, with a scan tool perform the Lamp Test for the instrument panel cluster (IPC) and observe the turn signal indicators.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.