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 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 left or right turn position, ground is applied through the respective left or right turn signal switch signal circuit to the body control module (BCM). The BCM then applies a pulsating voltage to the front and rear turn signal lamps through there respective voltage supply circuits. At the same time, the BCM sends a serial data message to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed.
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
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/Multifunction 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 Lamps 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/Multifunction 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 ground circuit terminal F and B+.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Left 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 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. Connect 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 and open/high resistance. If the circuit tests normal, replace the BCM.
6. Connect 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 and open/high resistance. If the circuit tests normal, replace the BCM.
7. If all circuits test normal, test or replace the turn signal/multifunction switch.
Turn Signal Lamps Malfunction
1. Ignition OFF, disconnect the X4 harness connect at the BCM.
2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
* B+ terminal 1
* B+ terminal 2
* B+ terminal 3
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuits test normal and the circuit fuse is open, test the appropriate control circuit terminal(s) listed below for a short to ground.
* Terminal 5 X4 for an open BCM 3 fuse
* Terminal 1 X5 and terminal 4 X5 for an open BCM 5 fuse
* Terminal 2 X5 for an open BCM 6 fuse
3. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
4. Test for less than 5.0 ohm between the appropriate ground circuit terminal listed below and ground.
* Front Turn Signal terminal C
* Outside Rearview Mirror terminal D
* Rear Turn Signal terminal G
• If greater than the specified range, test the ground circuit for an open/high resistance.
5. Connect a test lamp between the appropriate control circuit terminal listed below and ground.
* Front Turn Signal terminal A
* Outside Rearview Mirror terminal B
* Rear Turn Signal terminal A
6. 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.
7. If all circuits test normal, test or replace the turn signal bulb.
Component Testing
Turn Signal/Multifunction Switch
1. Ignition OFF, disconnect the harness connector X1 at the turn signal/multifunction switch.
2. Test for infinite resistance between the terminals listed below and the ground circuit terminal F with the switch in the neutral position.
* Signal terminal D
* Signal terminal E
• If not the specified value, replace the turn signal/multifunction switch.
Note: If the switch tests open in any switch position other than Off, test the switch signal circuits for a short to voltage before replacing the switch.
3. Test for less than 2.0 ohm between the signal terminal E and the ground terminal F with the switch in the left turn position.
• If greater than the specified range, replace the turn signal/multifunction switch.
4. Test for less than 2.0 ohm between the signal terminal D and the ground circuit terminal F with the switch in the right turn position.
• If greater than the specified range, replace the turn signal/multifunction switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Turn Signal Multifunction Switch Replacement (Service and Repair)
* Parking and Turn Signal Lamp Replacement (Service and Repair)
* Tail Lamp Replacement (Tail Lamp Replacement)
* Control Module References (Programming and Relearning) for BCM and IPC replacement, setup, and programming