Turn Signal Lamps and/or Indicators Malfunction
Turn Signal Lamps and/or Indicators Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
Ground is applied at all times 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. When a turn signal request is received by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed ON and OFF.
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the appropriate scan tool Turn/Hazard Lamp Command parameter while cycling the turn signal switch between the right and left positions. The parameter should change between ON and OFF when changing between the selected states.
• If the parameters do not change between the selected states, refer to Turn Signal Switch Malfunction.
2. Observe the right and left turn signal lamps while cycling the turn signal switch between the right and left positions. Verify the turn signal lamps turn ON and OFF when changing between the selected states.
• If the turn signal lamps do not cycle between the selected states, refer to Turn Signal Lamp Malfunction.
3. Command the Lamp Test ON and OFF with a scan tool. The left and right turn signal indicators should turn ON and OFF when changing between the commanded states.
• If the left and right turn signal indicators illuminate during the test, replace the BCM.
• If the left and right turn signal indicators do not illuminate during the test or remain illuminated at all times, replace the instrument cluster.
Circuit/System Testing
Turn Signal Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the turn signal/multifunction switch.
2. Test for less than 5 ohm between the ground circuit terminal and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify B+ is present between the signal circuit terminal B5 and ground.
• If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
4. If all circuits test normal, test or replace the turn signal/multifunction switch.
Turn Signal Lamp Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.
2. Test for less than 5 ohm between the ground circuit terminal G and ground.
• If more than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal A and ground.
4. Ignition ON, command the appropriate Turn Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded state.
• 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, replace the turn signal lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Park/Turn Signal/Side Marker Lamp Bulb Replacement (Service and Repair)
* Tail Lamp Bulb Replacement (Service and Repair)
* Tail Lamp Replacement (Service and Repair)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming