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
The body control module (BCM) controls the vehicle turn signals based on inputs from the turn signal/multifunction switch. With the turn signal/multifunction switch in the left turn position, a ground path is provided on the left turn signal switch signal circuit, indicating a left turn signal request. With the turn signal/multifunction switch in the right turn position, a ground path is provided on the right turn signal switch signal circuit, indicating a right turn signal request. When the specific request is seen, the BCM will pulse the respective turn signal lamp supply voltage circuits, illuminating the turn signal lamps.
When a turn signal request is seen by the BCM, a serial data message is sent 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 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 Display 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. Verify that a test lamp illuminates between the ground circuit terminal E 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 D 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 F for a short to ground. If the circuit tests normal, replace the BCM.
5. Install a 3 A fused jumper wire between the signal circuit terminal D and the ground circuit terminal E. 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. Install a 3 A fused jumper wire between the signal circuit terminal F and the ground circuit terminal E. 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 Lamp Malfunction
1. Ignition OFF, disconnect the harness connect X4 at the BCM.
2. Ignition ON, verify a test lamp illuminates between the B+ circuits 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 circuit tests normal and the fuse is open, test the appropriate control circuit(s) listed below for a short to ground.
* LT T/SIG Fuse - terminal 1 X5 and terminal 4 X5
* RT T/SIG Fuse - terminal 2 X5
* INT LIGHTS Fuse - terminal 5 X4
3. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.
4. Verify that a test lamp illuminates between the ground circuit terminal G and B+.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
5. Connect a test lamp between the control circuit terminal A and the ground circuit terminal G.
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 lamp.
Component Testing
Turn Signal/Multifunction Switch
1. Ignition OFF, disconnect the X1 harness connector at the turn signal/multifunction switch.
2. Test for infinite resistance between the signal terminals listed below and the ground circuit terminal E with the switch in the neutral position.
* Signal terminal D
* Signal terminal F
• 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 D and the ground terminal E 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 F and the ground terminal E with the switch in the left 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.
* Headlamp Bulb Replacement (Service and Repair)
* Rear Turn Signal Lamp Bulb Replacement (Service and Repair)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for BCM and IPC replacement, setup, and programming