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 at G200 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 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 ACTIVE and INACTIVE.
• 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. 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 Malfunction.
Circuit/System Testing
Turn Signal Lamp 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 inoperative 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 inoperative turn signal lamp.
5. Test for less than 5.0 ohms between the ground circuit terminal and ground.
* Front Park/Turn Signal Lamps terminal 1
* Rear Tail/Stop and Turn Signal Lamps terminal A
* Rear Turn Signal Lamp terminal B
* Tail/Stop Lamp terminal B
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the turn signal control circuit terminal and ground.
* Front Park/Turn Signal Lamps terminal 3
* Rear Tail/Stop and Turn Signal Lamps terminal C
* Rear Turn Signal Lamp terminal A
* Tail/Stop Lamp terminal C
7. Ignition ON, command the inoperative 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 inoperative turn signal lamp.
Turn Signal Switch Malfunction
1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
2. Verify that a test lamp illuminates between the listed ground circuit terminals and ground.
* Turn Signal/Multifunction Switch terminal F
* Turn Signal/Multifunction Switch terminal C
• 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.
* Left terminal E
* Right terminal D
• If not the specified value, test the appropriate signal circuit terminal for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the appropriate 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 appropriate 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.
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 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.
* 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 (SUV) (Tail/Turn Signal Lamp Replacement (SUV))Tail/Turn Signal Lamp Replacement (SUT) (Tail/Turn Signal Lamp Replacement (SUT))
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, programming, and setup.