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
The body control module (BCM) monitors three signal circuits from the headlamp switch. When the headlamp switch is in the AUTO position, all three signal circuits are open. When placed in the AUTO position, the BCM monitors inputs from the ambient light sensor to determine if headlamps are required or if daytime running lamps will be activated based on outside lighting conditions. When the headlamp switch is placed in the OFF position, the headlamp switch headlamps OFF signal circuit is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the headlamp switch in the PARK position, the headlamp switch park lamps ON signal circuit is grounded, indicating that the park lamps have been requested. When the headlamp switch is placed in the HEADLAMP position, both the headlamp switch park lamps ON signal circuit and the headlamp switch headlamps ON signal circuit are grounded. The BCM responds to the inputs by illuminating the park lamps and headlamps. When the low beam headlamps are requested, the BCM applies B+ to both low beam headlamp control circuits illuminating the low beam headlamps.
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
Connector End View Reference
Component Connector End Views Sunshade - Left (D6I)
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 Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Headlamps On Switch parameter while turning the headlamp switch ON and OFF. The parameter should change between Active and Inactive.
• If the parameter does not change between the commanded states, refer to Headlamp 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 Headlamp Switch Malfunction.
3. 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.
4. 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.
5. Command the Left Low Beam/Daytime Running Lamp 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 Low Beam/Daytime Running Lamp 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. 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. Command the All Indicators Test ON and OFF with a scan tool. The high beam indicator should turn ON and OFF when changing between the commanded states.
• If the high beam indicator does not turn ON and OFF when commanded, refer to High Beam Indicator Malfunction.
Circuit/System Testing
Headlamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, and wait 2 minutes. Test for less than 5 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. Ignition ON, verify the scan tool Automatic Headlamps Disable 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.
4. Verify the scan tool Park Lamps Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the K9 BCM.
5. Verify the scan tool Headlamps On 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.
6. Install a 3 A fused jumper wire between the signal circuit terminal 5 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.
7. Install a 3 A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Park Lamps 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 4 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.
9. If all circuits test normal, replace the S30 headlamp switch.
Turn Signal/Multifunction Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.
2. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, and wait 2 minutes. Test for less than 5 ohm between the ground circuit terminal 3 and ground.
• If greater then the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool High Beam Select 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 Headlamps Flash 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.
5. Install a 3 A fused jumper wire between the signal circuit terminal 2 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.
6. Install a 3 A fused jumper wire between the signal circuit terminal 4 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.
7. If all circuits test normal, replace the S78 turn signal/multifunction switch.
Headlamps Malfunction - Low Beam
1. Ignition OFF, disconnect the harness connector at the appropriate E13 headlamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 2 and ground.
• 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 1 and ground.
4. Ignition ON, command the appropriate Low Beam/Daytime Running 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 circuits test normal, replace the K9 BCM.
5. If all circuits test normal, replace the appropriate E13 headlamp.
Headlamps Malfunction - High Beam
1. Ignition OFF, disconnect the X2 harness connector at the X50A fuse block - underhood.
2. Connect a test lamp between the control circuit terminal 58 and B+.
3. Ignition 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 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. Ignition OFF, connect the X2 harness connector at the X50A fuse block - underhood.
5. Disconnect the harness connector at the appropriate E13 headlamp.
6. Ignition OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 2 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. Ignition 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 appropriate E13 headlamp.
High Beam Indicator Malfunction
1. Ignition ON, with a scan tool perform the Instrument Cluster All Indicators Test and observe the high beam indicator.
• If the high beam indicator illuminates during the test, replace the K9 BCM.
• If the high beam indicator does not illuminate during the test or remains illuminated at all times, replace the P16 instrument cluster.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Front Compartment Fuse Block Replacement Front Compartment Fuse Block Replacement
* Headlamp Bulb Replacement Service and Repair
* Headlamp Switch Replacement Service and Repair
* Turn Signal Switch Replacement Turn Signal Switch Replacement
* Control Module References Control Module References for BCM or Instrument Cluster replacement, setup, and programming