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 turn signals based on an input from the turn signal switch, part of the multifunction turn signal lever. The BCM receives an input from one of two signal circuits to determine which turn signal function is requested. When the turn signal lever is placed in the LEFT position, the left turn signal switch signal circuit is grounded indicating that left turn signal operation is requested. When the turn signal lever is placed in the RIGHT position, the right turn signal switch signal circuit is grounded indicating that right turn signal operation is requested.
When a turn signal input is received from the turn signal switch, the BCM will activate the appropriate turn signals. The BCM pulses voltage to the applicable turn signals via the turn signal lamp supply voltage circuits, illuminating the required turn signal lamps.
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Schematics)
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, observe the scan tool BCM Left Turn Signal parameter while turning the left turn signal ON and OFF with the turn signal multifunction lever. The parameter should change between On and Off.
• If the parameter does not change between the specified values, refer to Turn Signal Switch Circuit Malfunction.
2. Ignition ON, observe the scan tool BCM Right Turn Signal parameter while turning the right turn signal ON and OFF with the turn signal multifunction lever. The parameter should change between On and Off.
• If the parameter does not change between the specified values, refer to Turn Signal Switch Circuit Malfunction.
3. Command the appropriate turn signal lamp ON and OFF with a scan tool. The appropriate turn signal lamp should turn ON and OFF when changing between the commanded states.
• If the appropriate turn signal lamp does not cycle between the commanded states, refer to Turn Signal Circuit Malfunction.
Circuit/System Testing
Turn Signal Switch Circuit Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the turn signal multifunction lever.
2. Test for less than 5 ohms 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 BCM Left Turn Signal parameter is Off.
• 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 BCM Right Turn Signal parameter is Off.
• 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 the ground circuit terminal G. Verify the scan tool BCM Left Turn Signal parameter is On.
• 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 the ground circuit terminal G. Verify the scan tool BCM Right Turn Signal parameter is On.
• 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 lever.
Turn Signal Circuit Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp bulb.
2. Test for less than 10 ohms between the ground circuit terminal C (Front) or G (Rear) and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Install a test lamp between the signal circuit terminal A and ground.
4. Ignition ON, command the appropriate turn signal lamp ON and OFF with a scan tool. The appropriate turn signal lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the signal 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 bulb.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Parking and Turn Signal Lamp Bulb Replacement (Service and Repair)
* Rear Turn Signal Lamp Bulb Replacement (Rear Turn Signal Lamp Bulb Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming