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Headlamps Malfunction




Headlamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle
* Review Strategy Based Diagnosis Strategy Based Diagnosis
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions

Diagnostic Fault Information






Circuit/System Description

For headlamp operation, the body control module (BCM) monitors three signal circuits from the turn signal/multifunction switch. When the turn signal/multifunction switch is in the AUTO position, the three signal circuits are open and the BCM relies on the ambient light sensor input to turn the headlamps and daytime running lamps (DRLs) ON and OFF. When the turn signal/multifunction switch is placed in the OFF position, the turn signal/multifunction switch headlamps OFF signal circuit is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the turn signal/multifunction switch in the PARK LAMPS position, the turn signal/multifunction switch park lamps ON signal circuit is grounded, indicating that the park lamps have been requested. When the turn signal/multifunction switch is in the HEADLAMP position, both the turn signal/multifunction switch park lamps ON signal circuit and the turn signal/multifunction switch headlamps ON signal circuit are grounded. The BCM responds by commanding the park lamps and headlamps ON.

The high beam and flash to pass functions are contained within the turn signal/multifunction switch. The BCM provides the turn signal/multifunction switch with two signal circuits, the high beam signal circuit and the flash to pass signal circuit. When the low beam headlamps are ON and the turn signal/multifunction switch is placed in the high beam position, ground is applied to the BCM through the high beam signal circuit. The BCM responds to the high beam request by applying ground to the high beam relay control circuit which energizes the high beam relay. With the high beam relay energized, the switch contacts close allowing battery voltage to flow through the high beam fuses to the high beam control circuits illuminating the high beam headlamps.

When the turn signal/multifunction switch is momentarily placed in the flash to pass position, ground is applied to the BCM through the flash to pass signal circuit. The BCM responds by applying ground to the high beam relay control circuit which energizes the high beam relay illuminating the high beams for a brief moment or until the flash to pass switch is released.

Reference Information
Schematic Reference

* Headlights/Daytime Running Lights (DRL) Schematics Headlights/Daytime Running Lights (DRL) 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 Headlamps On Switch parameter while turning the low beam headlamps ON and OFF with the turn signal/multifunction switch. The parameter should change between Active and Inactive.

• If the parameter does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.

2. Observe the scan tool Automatic Headlamps Disable Switch parameter while applying and releasing the automatic lamp control disable switch. The parameter should change between Active and Inactive.

• If the parameter does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.

3. Observe the scan tool High Beam Select Switch parameter while applying and releasing the high beam select switch. The parameter should change between Active and Inactive.

• If the parameter does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.

4. Observe the scan tool Headlamps Flash Switch parameter while applying and releasing the flash to pass switch. The parameter should change between Active and Inactive.

• If the parameter does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.

5. Command the Left Headlamp Low Beam ON and OFF with a scan tool. The left low beam headlamp should turn ON and OFF when commanded.

• If the left low beam headlamp does not turn ON and OFF when commanded, refer to Headlamps Malfunction - Low Beam.

6. Command the Right Headlamp Low Beam ON and OFF with a scan tool. The right low beam headlamp should turn ON and OFF when commanded.

• If the right low beam headlamp does not turn ON and OFF when commanded, refer to Headlamps Malfunction - Low Beam.

7. Low beam headlamps ON, command the High Beams ON and OFF with a scan tool. The high beam headlamps should turn ON and OFF when commanded.

• If the high beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - High Beam.

8. Observe the high beam indicator while applying and releasing the high beam select switch. The high beam indicator should turn ON and OFF when changing between the commanded states.

• If the high beam indicator does not illuminate or remains illuminated at all times, replace the P16 instrument cluster.

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 then the specified range, test the ground circuit for an open/high resistance.

3. Vehicle in Service Mode, verify the scan tool Headlamps On Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K9 BCM.

4. Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 9 for a short to ground. If the circuit tests normal, replace the K9 BCM.

5. Verify the scan tool High Beam Select Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 11 for a short to ground. If the circuit tests normal, replace the K9 BCM.

6. Verify the scan tool Headlamps Flash Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 12 for a short to ground. If the circuit tests normal, replace the K9 BCM.

7. Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Headlamps On 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.

8. Install a 3 A fused jumper wire between the signal circuit terminal 9 and ground. Verify the scan tool Automatic Headlamps Disable 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.

9. Install a 3 A fused jumper wire between the signal circuit terminal 11 and ground. Verify the scan tool High Beam Select 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.

10. Install a 3 A fused jumper wire between the signal circuit terminal 12 and ground. Verify the scan tool Headlamps Flash 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.

11. If all circuits test normal, replace the S78 turn signal/multifunction switch.

Headlamps Malfunction - Low Beam
1. Vehicle OFF, disconnect the X1 harness connector at the K9 BCM.
2. Vehicle in Service Mode, verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Vehicle OFF, connect the X1 harness connector at the K9 BCM.
5. Disconnect the harness connector at the inoperative E13 headlamp.
6. Vehicle OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 5 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect a test lamp between the control circuit terminal 1 and ground.
8. Vehicle in Service Mode, command the appropriate Headlamp Low Beam 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 circuits test normal, replace the K9 BCM.

9. If all circuits test normal, replace the inoperative E13 headlamp.

Headlamps Malfunction - High Beam
1. Vehicle OFF, disconnect the X1 harness connector at the X50A fuse block - underhood.
2. Connect a test lamp between the control circuit terminal 18 and B+.
3. Vehicle in Service Mode, command the High Beams 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 ground. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

4. Vehicle OFF, connect the X2 harness connector at the X50A fuse block - underhood.
5. Disconnect the harness connector at the inoperative E13 headlamp.
6. Vehicle OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 4 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect a test lamp between the control circuit terminal 3 and ground.
8. Vehicle in Service Mode, low beam headlamps ON, command the High Beams 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 X50A fuse block - underhood.
• 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 X50A fuse block - underhood.

9. If all circuits test normal, replace the inoperative E13 headlamp.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests

* Instrument Cluster Replacement Service and Repair
* Headlamp Replacement Removal and Replacement
* Headlamp Bulb Replacement Service and Repair
* Turn Signal Multifunction Switch Replacement Turn Signal Multifunction Switch Replacement
* Accessory Wiring Junction Block Replacement Accessory Wiring Junction Block Replacement
* Control Module References Programming and Relearning for BCM replacement, setup, and programming

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