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 there respective voltage supply circuits. Ground for the left front turn signal lamp is supplied at G101. Ground for the right front turn signal lamp is supplied at G102. Ground for the rear turn signal lamps is supplied at G301 for the left and G302 for the right. For more detailed information concerning turn signal lamp operation refer to Exterior Lighting Systems Description and Operation .

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

Scan Tool Reference

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 the low current.

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 readings should toggle between ACTIVE and INACTIVE.

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

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

2. Ignition ON, observe the left turn signal lamps and turn signal indicators on the IPC while activating the left turn signals. The left turn signal lamps and indicators should illuminate and flash when turned ON.

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

3. Ignition ON, observe the right turn signal lamps and turn signal indicators on the IPC while activating the right turn signals. The right turn signal lamps and indicators should illuminate and flash when turned ON.

⇒	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 C4 harness connector at the turn signal/multifunction switch.
2. Test for less than 1 ohm of resistance between the ground circuit terminal G 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 F 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 F 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. Test for less than 1 ohm of resistance between the ground circuit 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 and the ground circuit.
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, test or 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 outage detection circuit terminal C 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 outage detection circuit terminal C 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 display test for the instrument panel cluster (IPC) and observe the turn signal lamp indicators.

Tail Lamp Assembly

1. Ignition OFF, disconnect the harness connector at the appropriate rear tail lamp assembly.
2. Test for infinite resistance between the outage detection terminal C and the ground terminal D at the tail lamp assembly.

⇒	If not the specified value, replace the tail lamp assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.