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.
Circuit/System Description
When the turn signal switch is placed in either the left or right position, a ground signal is completed from the turn signal switch to the BCM. When the hazard flasher switch is activated, a ground signal is completed from the turn signal/hazard switch to the BCM. The BCM then sends an ON-OFF voltage signal through the fuses to the appropriate turn signal and side repeater (export only) lamps or to all of the turn signal fuses for hazard operation. The driver door switch and passenger door switch also receive voltage from the BCM turn signal supply voltage circuits for the mirror turn signals. The door switches have no function or control of the mirror turn signals other than a pass through connection for the circuits. The audio chime is also activated when the turn signals are ON. The instrument panel cluster (IPC) receives the signals to activate the turn signal indicators over the GMLAN serial data system.
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
Programming and Relearning (Programming and Relearning)for scan tool information
Circuit/System Verification
1. Ignition ON, command the following ON and OFF with a scan tool. The respective turn signal lamp should turn on and off.
* LF Turn Signal
* LR Turn Signal
* RF Turn Signal
* RR Turn Signal
• If the turn signal lamp is always on or does not turn on, refer to Turn Signal Lamp Circuit Malfunction.
2. Ignition ON, observe the scan tool Left and Right Turn Signal Switch parameters while operating the turn signal switch to the left and right positions. The readings should change between Active and Inactive
• If not the specified values, refer to the Turn Signal Switch Circuit Test.
Circuit/System Testing
Turn Signal Lamp Circuit Malfunction
1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Ignition ON, verify a test lamp illuminates between the following B+ terminals and ground.
* B+ terminal 1
* B+ terminal 2
* 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 affected turn signal control circuits for a short to ground.
3. Ignition OFF, connect the X4 harness connector harness connector at the BCM.
4. Disconnect the harness connector at the affected turn signal lamp.
5. Verify that a test lamp illuminates between the affected ground circuit terminal and ground.
* Front terminal 1
* Rear terminal C
* Aux terminal A
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the affected turn signal control circuit terminal and ground.
* Front terminal 3
* Rear terminal H
* Aux terminal C
7. Ignition ON, command the affected 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.
8. If all circuits test normal, test or replace the affected turn signal bulb.
Turn Signal Switch Circuit Test
1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
2. Verify that a test lamp illuminates between the ground circuit terminal F and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool left and right turn signal parameters are Inactive.
• If not the specified value, test the affected signal circuit terminal for a short to ground. If the circuit tests normal, replace the BCM.
* Left terminal E
* Right terminal D
4. Install a 3A fused jumper wire between the affected signal circuit terminal and the ground circuit terminal F. Verify the scan tool left or right turn signal parameter is Active.
* Left terminal E
* Right terminal D
• If not the specified value, test the affected signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the turn signal/multifunction switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Parking and Turn Signal Lamp Replacement (SUT Rear) (Parking and Turn Signal Lamp Replacement (SUT Rear))Parking and Turn Signal Lamp Replacement (SUV) (Parking and Turn Signal Lamp Replacement (SUV))
* Tail/Turn Signal Lamp Replacement (SUT) (Tail/Turn Signal Lamp Replacement (SUT))Tail/Turn Signal Lamp Replacement (SUV) (Tail/Turn Signal Lamp Replacement (SUV))
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Programming and Relearning (Programming and Relearning)for BCM replacement, programming, and setup.