Headlamps Malfunction
Headlamps 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
For headlamp operation, the body control module (BCM) monitors 3 signal circuits from the turn signal/multifunction switch. When the turn signal/multifunction switch is in the AUTO position, the 3 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 2 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.
2. Verify the scan tool Headlamps On Switch parameter changes between Active and Inactive while commanding the headlamps ON and OFF with the turn signal/multifunction switch.
• If the parameter does not change
Refer to Headlamp Switch Malfunction.
• If the parameter changes
3. Verify the scan tool Automatic Headlamps Disable Switch parameter changes between Active and Inactive while commanding the automatic lamp control ON and OFF with the turn signal/multifunction switch.
• If the parameter does not change
Refer to Headlamp Switch Malfunction.
• If the parameter changes
4. Verify the scan tool Headlamps Flash Switch parameter changes between Active and Inactive while commanding the flash to pass ON and OFF with the turn signal/multifunction switch.
• If the parameter does not change
Refer to Turn Signal/Multifunction Switch Malfunction.
• If the parameter changes
5. Verify the scan tool High Beam Select Switch parameter changes between Active and Inactive while commanding the high beams ON and OFF with the turn signal/multifunction switch.
• If the parameter does not change
Refer to Turn Signal/Multifunction Switch Malfunction.
• If the parameter changes
6. Verify the left low beam headlamp lamp turns ON and OFF when commanding the Left Headlamp Low Beam ON and OFF with a scan tool.
• If the left low beam headlamp does not turn ON and OFF
Refer to Headlamps Malfunction - Low Beam.
• If the left low beam headlamp turns ON and OFF
7. Verify the right low headlamp turns ON and OFF when commanding the Right Headlamp Low Beam ON and OFF with a scan tool.
• If the right low beam headlamp does not turn ON and OFF
Refer to Headlamps Malfunction - Low Beam.
• If the right low beam headlamp turns ON and OFF
8. Low beam headlamps ON, verify the high beams turn ON and OFF when commanding the High Beams ON and OFF with a scan tool.
• If the high beams do not turn ON and OFF
Refer to Headlamps Malfunction - High Beam.
• If the high beams turn ON and OFF
9. Verify the high beam indicator on the instrument cluster turns ON and OFF while commanding the All Indicators Test ON and OFF with a scan tool.
• If the high beam indicator does not turn ON and OFF
Refer to High Beam Indicator Malfunction.
• If the high beam indicator turns ON and OFF
10. All OK.
Circuit/System Testing
Headlamp Switch Malfunction
1. Vehicle OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S78 turn signal/multifunction switch. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.
• If 10 ohms or greater
1. Vehicle OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Vehicle in Service Mode.
4. Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.
• If not Inactive
1. Vehicle OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for infinite resistance between the signal circuit terminal 9 and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If Inactive
5. Install a 3 A fused jumper wire between the signal circuit terminal 9 and the ground circuit terminal 6.
6. Verify the scan tool Automatic Headlamps Disable Switch parameter is Active.
• If not Active
1. Vehicle OFF, disconnect the X1 harness connector at the K9 body control module, vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit terminal 9 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If Active
7. Verify the scan tool Park Lamps Switch parameter is Inactive.
• If not Inactive
1. Vehicle OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for infinite resistance between the signal circuit terminal 7 and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If Inactive
8. Install a 3 A fused jumper wire between the signal circuit terminal 7 and the ground circuit terminal 6.
9. Verify the scan tool Park Lamps Switch parameter is Active.
• If not Active
1. Vehicle OFF, disconnect the X1 harness connector at the K9 body control module, vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit terminal 7 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If Active
10. Verify the scan tool Headlamps On Switch parameter is Inactive.
• If not Inactive
1. Vehicle OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for infinite resistance between the signal circuit terminal 2 and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If Inactive
11. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the ground circuit terminal 6.
12. Verify the scan tool Headlamps On Switch parameter is Active.
• If not Active
1. Vehicle OFF, disconnect the X1 harness connector at the K9 body control module, vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit terminal 2 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If Active
13. Test or replace the S78 turn signal/multifunction switch.
Turn Signal/Multifunction Switch Malfunction
1. Vehicle OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S78 turn signal/multifunction switch. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 6 and ground.
• If 10 ohms or greater
1. Vehicle OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Vehicle in Service Mode.
4. Verify the scan tool High Beam Select Switch parameter is Inactive.
• If not Inactive
1. Vehicle OFF, disconnect the X3 harness connector at the K9 body control module.
2. Test for infinite resistance between the signal circuit terminal 11 and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If Inactive
5. Install a 3 A fused jumper wire between the signal circuit terminal 11 and the ground circuit terminal 6.
6. Verify the scan tool High Beam Select Switch parameter is Active.
• If not Active
1. Vehicle OFF, disconnect the X3 harness connector at the K9 body control module, vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit terminal 11 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If Active
7. Verify the scan tool Headlamps Flash Switch parameter is Inactive.
• If not Inactive
1. Vehicle OFF, disconnect the X3 harness connector at the K9 body control module.
2. Test for infinite resistance between the signal circuit terminal 12 and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If Inactive
8. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the ground circuit terminal 6.
9. Verify the scan tool Headlamps Flash Switch parameter is Active.
• If not Active
1. Vehicle OFF, disconnect the X3 harness connector at the K9 body control module, vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit terminal 12 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If Active
10. Test or replace the S78 turn signal/multifunction switch.
Headlamps Malfunction - Low Beam
1. Vehicle OFF, disconnect the X1 harness connector at the K9 body control module, vehicle in Service Mode.
2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If the test lamp illuminates
3. Verify a test lamp illuminates between the B+ circuit terminal 3 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If the test lamp illuminates
4. Vehicle OFF, connect the X1 harness connector at the K9 body control module.
5. Vehicle OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 headlamp.
6. Test for less than 5 ohms between the ground circuit terminal 5 and ground.
• If 5 ohms or greater
1. Vehicle OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
7. Connect a test lamp between the control circuit terminal 1 and ground, vehicle in Service Mode.
8. Verify the test lamp turns ON and OFF when commanding the appropriate Headlamp Low Beam ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Vehicle OFF, disconnect the X4 harness connector at the K9 body control module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Vehicle OFF, disconnect the X4 harness connector at the K9 body control module, vehicle in Service Mode.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If the test lamp turns ON and OFF
9. Test or replace the appropriate E4 headlamp - low beam.
Headlamps Malfunction - High Beam
1. Vehicle OFF, disconnect the X2 harness connector at the X50A fuse block - underhood.
2. Connect a test lamp between the control circuit terminal 18 and B+, vehicle in Service Mode.
3. Verify the test lamp turns ON and OFF when commanding the High Beams ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Vehicle OFF, disconnect the X5 harness connector at the K9 body control module, vehicle in Service Mode.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Vehicle OFF.
4. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Vehicle OFF, disconnect the X5 harness connector at the K9 body control module.
2. Test for infinite resistance between the control circuit terminal and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 body control module.
• If the test lamp turns ON and OFF
4. Vehicle OFF, exterior lamps OFF, connect the X2 harness connector at the X50A fuse block - underhood.
5. Disconnect the harness connector at the appropriate E13 headlamp.
6. Test for less than 5 ohms between the ground circuit terminal 4 and ground.
• If 5 ohms or greater
1. Vehicle OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
7. Connect a test lamp between the control circuit terminal 3 and ground, vehicle in Service Mode.
8. Verify the test lamp turns ON and OFF when commanding the High Beams ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Vehicle OFF, disconnect the X1 harness connector at the X50A fuse block - underhood.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the X50A fuse block - underhood.
• If the test lamp is always ON
1. Vehicle OFF, disconnect the X1 harness connector at the X50A fuse block - underhood, vehicle in Service Mode.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the X50A fuse block - underhood.
• If the test lamp turns ON and OFF
9. Test or replace the appropriate E4 headlamp - high beam.
High Beam Indicator Malfunction
1. Vehicle in Service Mode.
2. Verify the high beam indicator turns ON and OFF when commanding the Instrument Cluster All Indicators Test ON and OFF with a scan tool.
• If the high beam indicator is always OFF or remains ON
Replace the P16 instrument cluster.
• If the high beam indicator turns ON and OFF
3. Replace the K9 body control module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the 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 and instrument cluster replacement, programming, and setup