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 vehicle mode switch in the SERVICE MODE or ON positions. 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 responds to the turn signal switch input by applying a pulsating voltage to the front and rear turn signal lamps through there respective control 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.
Diagnostic Aids
The tail lamp outage detection circuits are low current B+ circuits that will not illuminate a test lamp.
Reference Information
Schematic Reference
* Exterior Lights Schematics Exterior Lights Schematics
* Body Control System Schematics [1][2]Body Control Systems
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1
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. Vehicle in Service Mode, observe the scan tool Right Turn Signal Switch and Left Turn Signal Switch parameters while cycling the turn signal/multifunction 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. Command the Left Front Turn Signal Lamp ON and OFF with a scan tool. The left front turn signal should turn ON and OFF when changing between the commanded states.
• If the left front turn signal does not turn ON and OFF when changing between the commanded states, refer to Turn Signal Lamps Malfunction.
3. Command the Right Front Turn Signal Lamp ON and OFF with a scan tool. The right front turn signal should turn ON and OFF when changing between the commanded states.
• If the right front turn signal does not turn ON and OFF when changing between the commanded states, refer to Turn Signal Lamps Malfunction.
4. Command the Left Rear Turn Signal/Brake Lamp ON and OFF with a scan tool. The left rear turn signal should turn ON and OFF when changing between the commanded states.
• If the left rear turn signal does not turn ON and OFF when changing between the commanded states, refer to Turn Signal Lamps Malfunction.
5. Command the Right Rear Turn Signal/Brake Lamp ON and OFF with a scan tool. The right rear turn signal should turn ON and OFF when changing between the commanded states.
• If the right rear turn signal does not turn ON and OFF when changing between the commanded states, refer to Turn Signal Lamps Malfunction.
6. Observe the left and right turn signal lamps and turn signal indicators on the IPC while activating the left and right turn signals. The left and right turn signal lamps and indicators should illuminate and flash at a normal rate when turned ON.
• If the left and right turn signal lamps and indictors illuminate but flash in a rapid manner, refer to Tail Lamp Outage Detection Malfunction.
7. Command the Instrument Cluster Gauge Sweep 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 do not turn ON and OFF when commanded, refer to Turn Signal Indicators Malfunction.
Circuit/System Testing
Turn Signal/Multifunction Switch Malfunction
1. Vehicle OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.
2. Vehicle OFF, scan tool disconnected, all doors closed, all accessories OFF, and wait 2 minutes. Test for less than 10 ohm between the ground circuit terminal 6 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Vehicle in Service Mode, verify the scan tool Left Turn Signal Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 BCM.
4. Verify the scan tool Right Turn Signal Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the K9 BCM.
5. Install a 3 A fused jumper wire between the signal circuit terminal 4 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 K9 BCM.
6. Install a 3 A fused jumper wire between the signal circuit terminal 5 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 K9 BCM.
7. If all circuits test normal, replace the S78 turn signal/multifunction switch.
Turn Signal Lamps Malfunction
1. Vehicle OFF, disconnect the harness connector at the inoperative E4 turn signal lamp.
2. Vehicle OFF, exterior lamps OFF, test for less than 5 ohm between the appropriate ground circuit terminal listed below and ground:
* E4N park/turn signal lamp - left - terminal 1
* E4Y turn signal repeater lamp - left - terminal C
* E4P park/turn signal lamp - right - terminal 1
* E4Z turn signal repeater lamp - right - terminal C
* E42L tail lamp assembly - left - terminal 4
* E42R tail lamp assembly - right - terminal 4
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the appropriate control circuit terminal listed below and ground:
* E4N park/turn signal lamp - left - terminal 3
* E4Y turn signal repeater lamp - left - terminal A
* E4P park/turn signal lamp - right - terminal 3
* E4Z turn signal repeater lamp - right - terminal D
* E42L tail lamp assembly - left - terminal 1
* E42R tail lamp assembly - right - terminal 1
4. Vehicle in Service Mode, command the appropriate Turn Signal Lamp 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 K9 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 K9 BCM.
5. If all circuits test normal, replace the inoperative E4 turn signal lamp.
Tail Lamp Outage Detection Malfunction
1. Vehicle OFF, disconnect the harness connector at the inoperative E42 tail lamp assembly.
2. Vehicle in Service Mode, test for B+ between the signal circuit terminal 3 and ground.
• If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
3. Verify that a test lamp does not illuminate between the signal circuit terminal 3 and ground.
• If the test lamp illuminates, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
4. If all circuits test normal, replace the inoperative E42 tail lamp assembly.
Turn Signal Indicators Malfunction
1. Vehicle in Service Mode, with a scan tool perform the Instrument Cluster Gauge Sweep Test and observe the left and right turn signal indicators.
• If the left and right turn signal indicators illuminate during the test, replace the K9 BCM.
• If the left and right turn signal indicators do not illuminate during the test or remain illuminated at all times, replace the P16 instrument cluster.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Turn Signal Multifunction Switch Replacement Turn Signal Multifunction Switch Replacement
* Front Turn Signal Lamp Replacement Service and Repair
* Tail Lamp Replacement Tail Lamp Replacement
* Control Module References Programming and Relearning for BCM or Instrument Cluster replacement replacement, setup, and programming