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 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 (Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
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 Left Turn Signal Switch parameter while moving the turn signal switch from the center position to the left position. The value should be Inactive and change to Active.
• If the value does not change, refer to Turn Signal Switch Malfunction.
2. Ignition ON, observe the scan tool Right Turn Signal Switch parameter while moving the turn signal switch from the center position to the right position. The value should be Inactive and change to Active.
• If the value does not change, refer to Turn Signal Switch Malfunction.
3. Ignition ON, with the turn signal switch in the left position, observe the function of the E2LF side marker lamp-left front, the E4N park/turn signal lamp-left, the E4Y turn signal repeater lamp-left, E2LR side marker lamp-left rear, and the E4LR turn signal lamp-left rear. Each lamp should flash ON and OFF.
• a lamp is always OFF, refer to Turn Signal Lamps Malfunction.
4. Ignition ON, with the turn signal switch in the right position, observe the function of the E2RF side marker lamp-right front, the E4P park/turn signal lamp-right, the E4Z turn signal repeater lamp-right, E2RR side marker lamp-right rear, and the E4RR turn signal lamp-right rear. Each lamp should flash ON and OFF.
• a lamp is always OFF, refer to Turn Signal Lamps Malfunction.
5. Command the All Indicators 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 are always ON or always OFF, replace the P16 instrument cluster.
Circuit/System Testing
Turn Signal Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S78 turn signal/multi-function switch.
2. Test for less than 30 ohm between the ground circuit terminal 3 and ground.
• If greater than the specified range, 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 BCM.
4. 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 BCM.
5. 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 BCM.
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 BCM.
7. If all circuits test normal, test or replace the S78 turn signal/multi-function switch.
Turn Signal Lamps Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.
2. Test for less than 30 ohm between the ground circuit terminal listed below and ground.
* E2LF side marker lamp-left front terminal 2
* E4N park/turn signal lamp-left terminal G
* E4Y turn signal repeater lamp-left terminal 4
* E5E tail lamp-left terminal A
* E4LR turn signal lamp-left rear terminal B
* E2RF side marker lamp-right front terminal 2
* E4P park/turn signal lamp-right terminal G
* E4Z turn signal repeater lamp-right terminal 4
* E5E tail lamp right terminal A
* E4RR turn signal lamp-right rear terminal B
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal listed below and ground.
* E2LF side marker lamp-left front terminal 1
* E4N park/turn signal lamp-left terminal A
* E4Y turn signal repeater lamp-left terminal 16
* E5E tail lamp-left terminal E
* E5E tail lamp-left terminal D
* E4LR turn signal lamp-left rear terminal A
* E2RF side marker lamp-right front terminal 1
* E4P park/turn signal lamp-right terminal A
* E4Z turn signal repeater lamp-right terminal 16
* E5E tail lamp right terminal E
* E5E tail lamp right terminal D
* E4RR turn signal lamp-right rear terminal A
4. 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 turn signal lamp.
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 Bulb Replacement (TT2) (Front Turn Signal Lamp Bulb Replacement (TT2))Front Turn Signal Lamp Bulb Replacement (TT4) (Front Turn Signal Lamp Bulb Replacement (TT4))
* Tail Lamp Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM or instrument cluster replacement, setup and programming