Headlamps Malfunction - Low Beam (Without TT6, TT7, or TT8)
Headlamps Malfunction - Low Beam (Without TT6, TT7, or TT8)
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 ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 1.4-4.5 V depending on outside lighting conditions. The body control module (BCM) monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the daytime running lights ON. During low light conditions the BCM will command the low beam headlamps ON.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Component Connector End Views Connector End Views By Name
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
Circuit/System Verification
1. Ignition ON, observe the scan tool Ambient Light Sensor parameter. The reading should be between 1.4-4.5 V and change with ambient light changes.
• If greater or less than the specified range, refer to Ambient Light Sensor Malfunction.
2. Observe the scan tool Automatic Headlamp Disable Switch parameter while cycling the headlamp switch between the AUTOMATIC LIGHT and OFF positions. The parameter should cycle between Active and Inactive.
• If the value does not change, refer to Headlamp Switch Malfunction.
3. Observe the scan tool Headlamp ON Switch parameter while cycling the headlamp switch between the AUTOMATIC LIGHT and LOW BEAM ON position. The parameter should cycle between Active and Inactive.
• If the value does not change, refer to Headlamp Switch Malfunction.
4. Observe the function of the E4G headlamp-left low beam and the E4F headlamp-right low beam while commanding the low beam lamps ON and OFF with a scan tool. The E4G headlamp-left low beam and the E4F headlamp-right low beam should turn ON and OFF while changing between the commanded states
• If the E4G headlamp-left low beam and the E4F headlamp-right low beam are always ON or always OFF, refer to Low Beam Headlamp Malfunction.
Circuit/System Testing
Ambient Light Sensor Malfunction
1. Ignition OFF, disconnect the harness connector at the B10B ambient light/sunload sensor.
2. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 5 and ground.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
3. If all circuits test normal, replace the B10B ambient light/sunload sensor.
Headlamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Ignition OFF, test for less than 30 ohm between the ground circuit terminal 6 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, 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.
4. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the ground circuit terminal 6. Verify the scan tool Park Lamps Switch 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 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 4 and the ground circuit terminal 6. Verify the scan tool Headlamps On Switch 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. 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.
8. Install a 3 A fused jumper wire between the signal circuit terminal 5 and the ground circuit terminal 6. Verify the scan tool Automatic Headlamps Disable Switch 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, test or replace the S30 headlamp switch.
Low Beam Headlamp Malfunction
1. Ignition OFF, disconnect the harness X1 harness connector at the K9 BCM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal listed below and ground:
* B+ circuit terminal 3
* B+ circuit terminal 4
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Ignition OFF, connect the harness X1 harness connector at the K9 BCM.
4. Disconnect the inline harness connector at the appropriate E4 headlamp-low beam listed below:
* E4G headlamp-left low beam X115 inline harness connector
* E4F headlamp-right low beam X116 inline harness connector
5. Connect a test lamp between the control circuit terminal G and ground.
6. Ignition ON, command the low beam lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF while 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
7. If all circuits test normal, replace the headlamp bulb or the headlamp.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests
* Headlamp Replacement Headlamp Replacement
* Headlamp Switch Replacement Service and Repair
* Sun Load Temperature and Daytime Running Lamp Ambient Light Sensor Replacement Service and Repair
* Control Module References Control Module References