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
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 a pulsating voltage signal through the fuses to the appropriate turn signal and side repeater (European 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 (Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
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 scan tool Right Turn Signal Switch and Left Turn Signal Switch parameters while cycling the turn signal switch between the right and left positions. The readings should change between Active and Inactive.
• If the parameters do not change between the selected states, refer to Turn Signal Switch Malfunction.
2. Ignition ON, 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.
• 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 X1 at the turn signal/multifunction switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal F.
• 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 and Rear Turn Signal Switch parameter is INACTIVE.
• If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the BCM.
4. Verify the scan tool Right Front and Rear Turn Signal Switch parameter is INACTIVE.
• If not the specified value, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM.
5. Verify the scan tool Hazard Lamp Switch parameter is INACTIVE.
• If not the specified value, test the signal circuit terminal G for a short to ground. If the circuit tests normal, replace the BCM.
6. Install a 3 A fused jumper wire between the signal circuit terminal E and ground. Verify the scan tool Left Turn Signal Switch parameter is ACTIVE.
• 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. Install a 3 A fused jumper wire between the signal circuit terminal D and ground. Verify the scan tool Right Turn Signal Switch parameter is ACTIVE.
• 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.
8. Install a 3 A fused jumper wire between the signal circuit terminal G and ground. Verify the scan tool Hazard Lamp Switch parameter is ACTIVE.
• 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.
9. If all circuits test normal, test or replace the turn signal/multifunction switch.
Turn Signal Lamp Malfunction
1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Verify that a test lamp illuminates between the LT STOP TRN fuse B+ circuit terminal 1 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Verify that a test lamp illuminates between the RT STOP TRN fuse B+ circuit terminal 3 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Ignition OFF, reconnect the X4 harness connector at the BCM.
5. Disconnect the harness connector at the appropriate turn signal lamp.
6. Test for less than 5.0 ohm between the ground circuit terminal and ground.
* Park/Turn Signal Lamp - Left front terminal C - with X88/Z88
* Park/Turn Signal Lamp - Right front terminal A - with X88/Z88
* Turn Signal Lamp - Left and Right front terminal 3- with Z75
* Repeater Lamp - Left and Right front terminal 2 - with TR2
* Tail/Turn Signal Lamp - Left and Right rear terminal GRD - with X88
* Tail/Turn Signal Lamp - Left and Right rear terminal G- w/o X88
* Tail/Stop and Turn Signal Lamp - Left and Right Upper rear terminal GRD - with X88/Z75 - EXP - E52
* Tail/Stop and Turn Signal Lamp - Left and Right Lower rear terminal GRD - with X88/Z75 - EXP - E52
* Tail Lamp Circuit Board - Left and Right rear terminal D - with Z75 + E52
• If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect a test lamp between the appropriate turn signal control circuit terminal and ground.
* Park/Turn Signal Lamp - Left front terminal A - with X88/Z88
* Park/Turn Signal Lamp - Right front terminal D - with X88/Z88
* Turn Signal Lamp - Left and Right front terminal 1- with Z75
* Repeater Lamp - Left and Right front terminal 1- with TR2
* Tail/Turn Signal Lamp - Left and Right rear terminal MJR - with X88
* Tail/Turn Signal Lamp - Left and Right rear terminal A - w/o X88
* Tail/Stop and Turn Signal Lamp - Left and Right Upper rear terminal MJR - with X88/Z75 - EXP - E52
* Tail/Stop and Turn Signal Lamp - Left and Right Lower rear terminal MJR - with X88/Z75 - EXP - E52
* Tail Lamp Circuit Board - Left and Right rear terminal B - with Z75 + E52 - with EXP
* Tail Lamp Circuit Board - Left and Right rear terminal E - with Z75 + E52 - w/o EXP
8. Ignition ON, command the appropriate 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.
9. If all circuits test normal, test or replace the appropriate turn signal lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
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* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
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* Control Module References (Programming and Relearning) for BCM or IPC replacement, setup, and programming