Headlamps Malfunction
Headlamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category
Diagnostic Fault Information
Circuit/System Description
The headlamps may be turned ON in 3 different ways. First, when the driver places the headlamp switch in the ON position, normal operation occurs. Second, when the headlamp switch is placed in the AUTO position, automatic lamp control (ALC) operation occurs. During ALC control, the headlamps will be OFF in daylight conditions or in low/high beam operation in low light conditions. Third is in wiper activated headlamp (WAH) mode. Only when the wiper system is activated while the vehicle is in gear, the wiper blades have completed at least 3 cycles, and then a 35 second time period expires, will the body control module (BCM) switch from daytime running lamps (DRL) mode to headlamp mode during daylight conditions. When the gearshift lever is placed in the PARK or NEUTRAL position or if the wipers are turned OFF, normal manual or ALC operation will resume after approximately 60 seconds.
The LOW BEAM relay receives battery positive voltage directly from the battery. The BCM supplies a ground signal to the LOW BEAM relay for normal headlight operation. The BCM also supplies voltage to the HIGH BEAM relay for high beam headlight operation. When the driver places the headlamp switch in the ON position and the dimmer switch is in the low beam position, the LOW BEAM relay supplies current flow through the left and right low beam headlamp fuses to both low beam headlamps. When activated, the dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-pass (FTP) position. The BCM then energizes the HIGH BEAM relay which supplies current flow through the left and right hi beam headlamp fuses to both high beam headlamps. With the headlights in the low beam position, the high beams may be momentarily turned ON or flashed by activating the FTP portion of the switch.
The instrument panel cluster (IPC) illuminates the high beam indicator when the BCM detects that the high beams are requested. The IPC receives a serial data message from the BCM requesting illumination.
The Headlamps On at Exit and Perimeter Lighting modes can be adjusted using the steering wheel controls to select the desired function as displayed in the driver information center (DIC). The Headlamps On at Exit selection will allow the driver to customize the period of time that the headlamps remain illuminated upon exiting the vehicle. This period can be adjusted from 0-180 seconds. The Perimeter Lighting feature allows the driver to select if they desire the headlamps and backup lamps to illuminate when the door UNLOCK button on the key fob is activated. This feature can be turned ON or OFF by using the DIC steering wheel control buttons.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Diagrams)
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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Auto Hdlp. Disable Sw. parameter while cycling the headlamp switch between the Auto and Off positions. The parameter should cycle between Active and Inactive.
• If the parameter does not cycle between the specified values, Refer to Headlamp Switch Malfunction.
2. Observe the scan tool Headlamp Switch parameter while cycling the headlamp switch between the Auto and Head position. The parameter should cycle between Active and Inactive.
• If the parameter does not cycle between the specified values, Refer to Headlamp Switch Malfunction.
3. With the headlamps ON, observe the scan tool Flash to Pass Switch parameter while pulling and releasing the flash to pass switch. The parameter should cycle between Active and Inactive.
• If the parameter does not cycle between the specified values, Refer to Turn Signal/Multifunction Switch Malfunction.
4. With the headlamps ON, observe the scan tool High Beam Select Switch parameter while switching the headlamp dimmer switch between the low and high beam positions. The parameter should cycle between Active and Inactive.
• If the parameter does not cycle between the specified values, Refer to Turn Signal/Multifunction Switch Malfunction.
5. Command the Low Beams ON and OFF with a scan tool. Verify the low beam headlamps turn ON and OFF.
• If the low beam headlamps do not cycle between the commanded states, Refer to Low Beam Headlamp Malfunction.
6. Command the High Beams ON and OFF with a scan tool. Verify the low beam headlamps turn ON and OFF.
• If the high beam headlamps do not cycle between the commanded states, Refer to High Beam Headlamp Malfunction.
Circuit/System Testing
Headlamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between the ground circuit terminal 4 and B+.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Headlamp Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 6 for a short to ground. If the circuit tests normal, replace the BCM.
4. Verify the scan tool Auto Hdlp. Disable Sw. parameter is Inactive.
• If not the specified value, test the signal circuit terminal 8 for a short to ground. If the circuit tests normal, replace the BCM.
5. Install a 3A fused jumper wire between the signal circuit terminal 6 and ground. Verify the scan tool Headlamp Switch parameter is Active.
• If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
6. Install a 3A fused jumper wire between the signal circuit terminal 8 and ground. Verify the scan tool Auto Hdlp. Disable Sw. parameter is Active.
• If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
7. If all circuits test normal, test or replace the headlamp switch.
Turn Signal/Multifunction Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the turn signal/multifunction switch.
2. Ignition OFF, test for less than 5.0 ohms between the ground circuit listed below and ground:
* RPO HP7 - Terminal A
* All others - Terminal G
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Flash to Pass Switch parameter is Inactive.
• If not the specified value, test the signal circuit listed below for a short to ground. If the circuit tests normal, replace the BCM.
* RPO HP7 -Terminal C
* All others - Terminal J
4. Verify the scan tool High Beam Select Switch parameter is Inactive.
• If not the specified value, test the signal circuit listed below for a short to ground. If the circuit tests normal, replace the BCM.
* RPO HP7 - Terminal B
* All others - Terminal H
5. Install a 3A fused jumper wire between the signal circuit listed below and ground. Verify the scan tool Flash to Pass Switch parameter is Active.
* RPO HP7 - Terminal C
* All others - Terminal J
• If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
6. Install a 3A fused jumper wire between the signal circuit listed below and ground. Verify the scan tool High Beam Select Switch parameter is Active.
* RPO HP7 - Terminal B
* All others - Terminal H
• If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.
7. If all circuits test normal, test or replace the turn signal/multifunction switch.
Low Beam Headlamp Malfunction
1. Ignition OFF, disconnect the LOW BEAM relay.
2. Ignition ON, connect a test lamp between B+ and the control circuit terminal 86.
3. Command the low beam headlamps 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 BCM.
• If the test lamp is always OFF, test the control circuit for a open/high resistance or short to voltage. If the circuit tests normal, replace the BCM.
4. Connect a test lamp between the B+ circuit terminal 85 and ground. The test lamp should be ON.
• If the test lamp is OFF, test the B+ circuit for a open/high resistance or short to ground.
5. Connect a test lamp between the B+ circuit terminal 30 and ground. The test lamp should be ON.
• If the test lamp is OFF, test the B+ circuit for a open/high resistance or short to ground.
6. Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. The low beam headlamps should illuminate.
• If the low beam headlamps do not illuminate, test the low beam control circuit for an open/high resistance or short to ground.
7. If all circuits test normal, replace the LOW BEAM relay
High Beam Headlamp Malfunction
1. Ignition OFF, disconnect the HIGH BEAM relay.
2. Ignition ON, connect a test lamp between B+ and the control circuit terminal 86.
3. Command the high beam headlamps 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 BCM.
• If the test lamp is always OFF, test the control circuit for a open/high resistance or short to voltage. If the circuit tests normal, replace the BCM.
4. Connect a test lamp between the B+ circuit terminal 85 and ground. The test lamp should be ON.
• If the test lamp is OFF, test the B+ circuit for a open/high resistance or short to ground.
5. Connect a test lamp between the B+ circuit terminal 30 and ground. The test lamp should be ON.
• If the test lamp is OFF, test the B+ circuit for a open/high resistance or short to ground.
6. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. The high beam headlamps should illuminate.
• If the high beam headlamps do not illuminate, test the high beam control circuit for an open/high resistance or short to ground.
7. If all circuits test normal, replace the HIGH BEAM relay.
Component Testing
Headlamp Switch
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for infinite resistance between the signal terminal 8 and the ground terminal 4 with the switch in the Auto position.
• If not the specified value, replace the headlamp switch.
3. Test for infinite resistance between the signal terminal 6 and the ground terminal 4 with the switch in the Auto position.
• If not the specified value, replace the headlamp switch.
4. Test for less than 2.0 ohms between the signal terminal 8 and the ground terminal 4 with the switch in the Off position.
• If not the specified value, replace the headlamp switch.
5. Test for less than 2.0 ohms between the signal terminal 6 and the ground terminal 4 with the switch in the Headlamp position.
• If not the specified value, replace the headlamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Switch Replacement (Service and Repair)
* Headlamp Bulb Replacement (HIGH Beam) (Service and Repair)Headlamp Bulb Replacement (Low Beam) (Service and Repair)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming