Turn Signal Lamps and/or Indicators Malfunction

Turn Signal Lamps and/or Indicators Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach
* Diagnostic Procedure Instructions provides an overview of each diagnostic category Diagnostic Fault Information

Diagnostic Fault Information






Circuit/System Description

The body control module (BCM) controls the vehicle turn signals based on inputs from the turn signal/multifunction switch. With the turn signal/multifunction switch in the left turn position, a ground path is provided on the left turn signal switch signal circuit, indicating a left turn signal request. With the turn signal/multifunction switch in the right turn position, a ground path is provided on the right turn signal switch signal circuit, indicating a right turn signal request. When the specific request is seen, the BCM will pulse the respective turn signal lamp supply voltage circuits, illuminating the turn signal lamps.

When a turn signal request is seen by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed.

Circuit/System Verification

1. Ignition ON, view the scan tool Left Turn Signal Switch parameter while using the turn signal/multifunction switch left turn signal on and off. The parameter should cycle between Active and Inactive.

• If the parameter does cycle between the specified values, refer to Turn Signal/Multifunction Switch Circuit Malfunction.

2. View the scan tool Right Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the signal on and off. The parameter should cycle between Active and Inactive.

• If the parameter does cycle between the specified values, refer to Turn Signal/Multifunction Switch Circuit Malfunction.

3. Command the following ON and OFF with a scan tool. The respective turn signal should illuminate.

• LF Turn Signal
• RF Turn Signal
• LR Turn Signal
• RR Turn Signal

• If the turn signal does not illuminate, refer to Turn Signal Circuit Malfunction.

4. With the turn signal/multifunction switch in the left turn position, verify the left turn signal indicator is illuminated on the IPC.

• If the indicator is not illuminated, replace the IPC.

5. With the turn signal/multifunction switch in the right turn position, verify the right turn signal indicator is illuminated on the IPC.

• If the indicator is not illuminated, replace the IPC.

Circuit/System Testing

Turn Signal/Multifunction Switch Circuit Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
2. Test for less than 1.0 ohm of resistance between the ground circuit terminal E 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 D 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 F 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 D and the ground circuit terminal E. 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 and open/high resistance. If the circuit tests normal, replace the BCM.

6. Install a 3A fused jumper wire between the signal circuit terminal F and the ground circuit terminal E. 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 and 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 Circuit Malfunction

1. Ignition OFF, disconnect the X4 harness connect at the BCM.

2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
• B+ terminal 1
• B+ terminal 3

• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the B+ circuit and the respective turn signal circuits for a short to ground.

3. Ignition OFF, disconnect the harness connector at the turn signal lamp.
4. Test for less than 1.0 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.

5. Connect a test lamp between the control circuit terminal A and the ground circuit terminal G.
6. Ignition ON, command the affected turn signal 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. o 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.

7. If all circuits test normal, test or replace the turn signal lamp.

Component Testing

Turn Signal/Multifunction Switch

1. Ignition OFF, disconnect the harness connector X1 at the turn signal/multifunction switch.
2. Test for infinite resistance between the following terminals and the ground circuit terminal E with the switch in the neutral position.
• Signal terminal D
• Signal terminal F

• If not the specified value, replace the turn signal/multifunction switch.

3. Test for less than 2.0 ohms of resistance between the signal circuit terminal D and the ground circuit terminal E with the switch in the left turn position.

• If greater than the specified range, replace the turn signal/multifunction switch.

4. Test for less than 2.0 ohms of resistance between the signal circuit terminal F and the ground circuit terminal E with the switch in the left turn position.

• If greater than the specified range, replace the turn signal/multifunction switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Turn Signal Multifunction Switch Replacement
* Parking and Turn Signal Lamp Replacement