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
The FRT/TRN/HAZ/CRTSY/MIRR and REAR/TRN/HAZ fuses in the underhood fuse block supplies B+ to the body control module (BCM). When the turn signal switch is placed in either the left or right position, a signal is sent to the BCM to illuminate the desired turn signal lamps. The BCM has an internal flasher that sends an ON-OFF voltage signal to either the left or right turn signals and their instrument panel cluster (IPC) indicator. When the hazard switch is pressed, a separate ground signal is sent to the BCM to activate and flash all turn signal lamps including both IPC turn indicators. The front and rear turn signals are grounded at G105, G350 and G340. The IPC illuminates the TURN SIGNAL ON indicator in the driver information center (DIC) when the IPC determines that the turn signal is active for more than 1.2 km (0.75 mi). The BCM sends a class 2 message to the radio in order to activate the audible warning
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference
Component Connector End Views (Component Connector End 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 Right and Left Turn Signal Switch parameters while cycling the turn signal switch between the left and right positions. The readings should toggle between ON and OFF.
• If the readings do not change between the commanded states, refer to Turn Signal Switch Malfunction.
• If the readings change between the commanded states and the IPC turn signal indicators are inoperative, refer to Turn Signal Indicators Malfunction.
2. Observe the left turn signal lamps and turn signal indicators on the IPC while activating the left turn signals. The left turn signal lamps and indicators should illuminate and flash when turned ON.
• If the left turn signal lamps and indictors illuminate but flash in a rapid manner, refer to Turn Signal Lamps Malfunction.
3. Observe the right turn signal lamps and turn signal indicators on the IPC while activating the right turn signals. The right turn signal lamps and indicators should illuminate and flash when turned ON.
• If the right turn signal lamps and indictors illuminate but flash in a rapid manner, refer to Turn Signal Lamps Malfunction.
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 ohms between the ground circuit terminal B9 and ground.
• If greater than the specified range, test the ground circuit for a short to voltage or an open/high resistance.
3. Ignition ON, verify a test lamp illuminates between the turn signal/multifunction switch signal circuit terminal B5 and ground.
• If a test lamp does not illuminate, test the signal circuit terminal B5 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 Lamps Malfunction
1. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the appropriate ground circuit terminal listed below and ground.
* Left front turn signal ground circuit terminal C
* Right front turn signal ground circuit terminal C
* Left rear turn signal ground circuit terminal G
* Right rear turn signal ground circuit terminal G
• If greater than the specified range, test the ground circuit for a short to voltage or an open/high resistance.
3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.
* Left front turn signal control circuit terminal A
* Right front turn signal control circuit terminal A
* Left rear turn signal control circuit terminal A
* Right rear turn signal control circuit terminal A
4. Command the appropriate Turn Signal Lamp 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.
5. If all circuits test normal, replace the appropriate turn signal lamp.
Turn Lamp Indicator Malfunction
Ignition ON, with a scan tool perform the Display Test for the instrument panel cluster (IPC) and observe the turn signal lamp indicators.
If the turn signal lamp indicators illuminate during the test, replace the BCM.
If the turn signal lamp indicators do not illuminate during the test or remain illuminated at all times, replace the IPC.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Park/Turn Signal Lamp Bulb Replacement (Service and Repair)
* Tail Lamp Bulb 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.