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 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 cluster 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 Sunshade - Left
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
Ignition ON, observe the scan tool Right Turn Signal Switch parameter and Left Turn Signal Switch parameter while switching the S78 Turn Signal/Multifunction 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 instrument cluster turn signal indicators are inoperative, refer to Turn Signal Indicators Malfunction.
Circuit/System Testing
Turn Signal Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S78 Turn Signal/Multifunction Switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 3.
• 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 1 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
4. Verify the scan tool Right Turn Signal Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 7 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
5. Install a 3 A fused jumper wire between the signal circuit terminal 1 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 Body Control Module.
6. Install a 3 A fused jumper wire between the signal circuit terminal 7 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 Body Control Module.
7. If all circuits test normal, test or replace the S78 Turn Signal/Multifunction Switch.
Turn Signal Lamps Malfunction
1. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
2. Disconnect the negative terminal of the C1 Battery.
3. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.
* E4LF Turn Signal Lamp - Left Front ground circuit terminal 1
* E4RF Turn Signal Lamp - Right Front ground circuit terminal 1
* E4LR Turn Signal Lamp - Left Rear ground circuit terminal 3
* E4RR Turn Signal Lamp - Right Rear ground circuit terminal 3
* E4Y Turn Signal Repeater Lamp - Left ground circuit terminal 1
* E4Z Turn Signal Repeater Lamp - Right ground circuit terminal 1
• If greater than the specified range, test the ground circuit for an open/high resistance.
4. Reconnect the negative terminal to the C1 Battery.
5. Connect a test lamp between the appropriate control circuit terminal listed below and ground.
* E4LF Turn Signal Lamp - Left Front control circuit terminal 2
* E4RF Turn Signal Lamp - Right Front control circuit terminal 2
* E4LR Turn Signal Lamp - Left Rear control circuit terminal 2
* E4RR Turn Signal Lamp - Right Rear control circuit terminal 2
* E4Y Turn Signal Repeater Lamp - Left ground circuit terminal 2
* E4Z Turn Signal Repeater Lamp - Right ground circuit terminal 2
6. Command with 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 Body Control Module.
• 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 Body Control Module.
7. If all circuits test normal, replace the appropriate turn signal lamp assembly.
Turn Signal Indicators Malfunction
Ignition ON, command the All Indicators test ON and OFF with the scan tool, verify both turn signal indicators changes between turn ON and OFF.
If both turn signal indicators changes between illuminate and not illuminate during the test, replace the K9 Body Control Module.
If one or both turn signal indicators do not illuminate during the test or remain illuminated at all times, replace the P16 Instrument Cluster.
Component Testing
Turn Signal Switch
1. Ignition OFF, disconnect the harness connector at the S78 Turn Signal/Multifunction Switch.
2. Remove S78 Turn Signal/Multifunction Switch.
3. Test for greater than 500 kohms between signal terminal 1 and ground terminal 3.
• If less than the specified value, replace the S78 Turn Signal/Multifunction Switch.
4. Test for greater than 500 kohms between signal terminal 7 and ground terminal 3.
• If less than the specified value, replace the S78 Turn Signal/Multifunction Switch.
5. Push the S78 Turn Signal/Multifunction Switch turn left. Test for less than 5 ohms between signal terminal 1 and ground terminal 3.
• If greater than the specified value, replace the S78 Turn Signal/Multifunction Switch.
6. Push the S78 Turn Signal/Multifunction Switch turn right. Test for less than 5 ohms between signal terminal 7 and ground terminal 3.
• If greater than the specified value, replace the S78 Turn Signal/Multifunction Switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Headlamp Replacement Headlamp Replacement
* Front Side Turn Signal Lamp Replacement Service and Repair
* Tail Lamp Replacement Service and Repair
* Control Module References Programming and Relearning for BCM or instrument cluster replacement, setup, and programming