Turn Signal Lamps and/or Indicators Malfunction
Turn Signal Lamps and/or Indicators Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
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 control 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.
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, view the scan tool Left Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the 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 right 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.
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 harness connector at the turn signal/multifunction switch.
2. Test for less than 1.0 ohm between the ground circuit listed below and ground:
* RPO HP7 - Terminal F
* All others - Terminal M
• 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 listed below for a short to ground. If the circuit tests normal, replace the BCM.
* RPO HP7 - Terminal D
* All others - Terminal K
4. Verify the scan tool Right Turn Signal Switch parameter is Inactive.
• If not the specified value, test the signal circuit listed below for a short to ground. If the circuit tests normal, replace the BCM.
* RPO HP7 - Terminal E
* All others - Terminal L
5. Install a 3A fused jumper wire between the signal circuit listed below and the ground circuit . Verify the scan tool Left Turn Signal Switch parameter is Active.
* RPO HP7 - Terminal D
* All others - Terminal K
• 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 listed below and the ground circuit . Verify the scan tool Right Turn Signal Switch parameter is Active.
* RPO HP7 - Terminal E
* All others - Terminal L
• 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 connector at the BCM.
2. Ignition ON, verify a test lamp illuminates between the 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 appropriate turn signal circuits for a short to ground.
3. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.
4. Test for less than 5.0 ohm between the ground circuit listed below and ground:
* Front turn signal - Terminal B
* Front park/turn signal - Terminal 1
* Rear turn signal - Terminal B
• If greater than the specified range, test the ground circuit for an open/high resistance.
5. Connect a test lamp between the control circuit terminals listed below and the ground circuit:
* Front turn signal - Terminal A
* Front park/turn signal - Terminal 3
* Rear turn signal - Terminal H
6. Ignition ON, command the appropriate 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.
• 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 appropriate turn signal lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Park/Turn Signal Lamp Bulb Replacement (Service and Repair)
* Tail Lamp Bulb Replacement (Back Up Turn Signal) (Service and Repair)Tail Lamp Bulb Replacement (Stop Lamp) (Service and Repair)
* Control Module References (Programming and Relearning) for BCM and IPC replacement, setup, and programming