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
With the ignition switch in the RUN position, the turn signal lamps will illuminate when the driver places the turn signal switch in the right or left positions. The instrument panel module (IPM) monitors the signal circuit of the turn signal/multifunction switch. The IPM relays the turn signal switch status to the rear integration module (RIM) via the GMLAN serial data circuit. The RIM uses the status of the turn signal switch to command the turn signals ON and OFF. The RIM controls both front and rear turn signals. The IPM also sends a message via GMLAN to the instrument panel cluster (IPC) to enable the turn signal indicators located in the IPC ON and OFF depending on the position of the turn signal switch. Voltage is supplied to the front and rear turn signals by the RIM. Ground is provided to the front turn signals at G104. The rear turn signals are grounded at G401 and G402. The turn signal/multifunction switch is grounded at G200.
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)
Diagnostic Aids
The tail lamp outage detection circuits are low current B+ circuits supplied by the BCM. For purposes of testing, a test lamp connected between the outage detection circuit and ground will not illuminate due to the low current.
Circuit/System Verification
1. Ignition ON, observe the scan tool right and left turn/hazard lamp command 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 turn signal indicators are inoperative, refer to Turn Signal Indicators Malfunction.
2. Ignition ON, 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 Tail Lamp Outage Detection Malfunction.
3. Ignition ON, 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 left turn signal lamps and indictors illuminate but flash in a rapid manner, refer to Tail Lamp Outage Detection Malfunction.
Circuit/System Testing
Turn Signal Switch Malfunction
1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal G.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool left front turn/hazard command 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 IPM.
4. Verify the scan tool right front turn/hazard command 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 IPM.
5. Install a 3A fused jumper wire between the signal circuit terminal F and ground. Verify the scan tool left front turn/hazard command 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 IPM.
6. Install a 3A fused jumper wire between the signal circuit terminal H and ground. Verify the scan tool right front turn/hazard command 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 IPM.
7. 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/repeater lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit and the ground circuit.
4. Command the appropriate turn signal lamp ON and OFF with the turn signal/multifunction switch. 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 RIM.
• 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 RIM.
5. If all circuits test normal, test or replace the appropriate turn signal lamp assembly.
Tail Lamp Outage Detection Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate rear tail lamp assembly.
2. Ignition ON, test for B+ between the outage detection circuit terminal C and ground.
• If the measured voltage is less than B+, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the RIM.
3. Ignition ON, connect a test lamp between the outage detection circuit terminal C and ground. The test lamp should not Illuminate.
• If the test lamp illuminates, test the signal circuit for a short to voltage. If the circuit tests normal, replace the RIM.
4. If all circuits test normal, test or replace the tail lamp assembly.
Turn Signal Indicators 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 IPM.
If the turn signal lamp indicators do not illuminate during the test or remain illuminated at all times, replace the IPC.
Component Testing
Tail Lamp Assembly
1. Ignition OFF, disconnect the harness connector at the appropriate rear tail lamp assembly.
2. Test for infinite resistance between the outage detection terminal C and the ground terminal D at the tail lamp assembly.
• If not the specified value, replace the tail lamp assembly.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Front Parking and Turn Signal and Fog Lamp Assembly Replacement (Service and Repair)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for IPC or IPM replacement, setup, and programming