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