Headlamps Malfunction (w/o TT6)
Headlamps Malfunction (w/o TT6)
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 HDM and high beam relay receive battery positive voltage directly from the battery. The BCM supplies a 100% duty cycle PWM ground signal to the HDM for automatic headlight control and normal headlight operation. The BCM also supplies ground to the high beam relay coil for high beam headlight operation. When the driver places the headlamp switch in the HEADLAMP position and the dimmer switch is in the low beam position, the HDM switches to full output sending current flow through the left and right low beam headlamp fuses to both low beam headlamps. 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 from G102 to deactivate the low beam headlights and activate the high beam headlights. 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.
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 Views)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
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. Ignition ON, observe the scan tool Headlamp Switch parameter while cycling the headlamp switch between the AUTO and HEAD ON position. The parameter should cycle between Active and Inactive.
• If the parameter does not cycle between the specified values, refer to the Headlamp Switch Malfunction.
2. Observe the headlamps while cycling the headlamp switch between the AUTO and HEAD ON position. The low beam headlamps should turn ON and OFF.
• If 1 or both of the low beam headlamps do not turn ON and OFF, refer to the Headlamp Malfunction - Low Beam.
3. With the headlamps ON, observe the scan tool High Beam Switch parameter while switching the headlamp dimmer switch between the LOW and HI BEAM positions. The parameter should cycle between ON and OFF.
• If the parameter does not cycle between the specified values, refer to the Dimmer Switch Malfunction.
4. With the headlamps ON, observe the headlamps while switching the headlamp dimmer switch between the LOW and HI BEAM positions. The high beam headlamps should turn ON and OFF.
• If 1 or both of the high beam headlamps do not turn ON and OFF, refer to the Headlamp Malfunction - High Beam
5. Ignition ON, Headlamp ON, with a scan tool, verify the headlamp Flash to Pass parameter toggles between ON and OFF when pulling and releasing the dimmer switch.
• If the parameter does not change between the commanded states, refer to Dimmer Switch Malfunction.
6. Ignition ON, Headlamps ON, pull and release the flash to pass switch. The high beam headlamps should flash ON and OFF.
• If the headlamps do not turn ON and OFF, refer to Headlamp Malfunction - High Beam.
Circuit/System Testing
Headlamp Switch Malfunction
1. Ignition OFF, disconnect the X3 harness connector at the turn signal multifunction switch.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal
• 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 headlamp on switch signal circuit terminal L for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the headlamp on switch signal circuit terminal L and the ground circuit terminal K. Verify the scan tool Headlamp Switch parameter is Active.
• If not the specified value, test the headlamp on switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the turn signal multifunction switch.
Dimmer Switch Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the turn signal multifunction switch.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal A.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool High Beam Switch parameter is OFF.
• If not the specified value, test the high beam switch signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the high beam switch signal circuit terminal C and the ground circuit terminal A. Verify the scan tool High Beam Switch parameter is ON.
• If not the specified value, test the high beam switch signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. Ignition ON, verify the scan tool Flash to Pass switch parameter is OFF.
• If not the specified value, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the BCM.
6. Install a 3A fused jumper wire between the signal circuit terminal B and the ground circuit terminal A. Verify the scan tool Flash to Pass Switch parameter is ON.
• 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 BCM.
7. If all circuits test normal, test or replace the turn signal/multifunction switch.
Headlamp Malfunction - Low Beam
1. Ignition OFF, disconnect the HDM relay.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 6.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 5 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
4. 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. If the circuit tests normal, and the B+ circuit fuse is open, test the low beam headlamp control circuit terminal 4 for a short to ground.
5. Disconnect the harness connector at the inoperative headlamp.
6. Verify that a test lamp illuminates between B+ and the low beam headlamp ground circuit terminal B.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the headlamp.
8. Connect a 15A fused jumper wire between the B+ circuit terminal 2 and the low beam headlamp control circuit terminal 4. Verify the low beam headlamps are illuminated at full intensity.
• If the low beam headlamps do not illuminate at full intensity, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the inoperative headlamp.
9. If all circuits test normal, test or replace the HDM relay.
Headlamp Malfunction - High Beam
1. Ignition OFF, disconnect the HI HEADLAMP relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground.
4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
5. Ignition OFF, disconnect the harness connector at the inoperative HI BEAM headlamp.
6. Test for less than 5.0 ohms between the ground circuit terminal B and ground.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the HI BEAM headlamp.
8. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the high beam headlamps are ON.
• If the high beam headlamps do not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the inoperative headlamp.
9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 87.
10. Turn the high beam headlamps ON and OFF. 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 short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
11. If all circuits test normal, test or replace the HI HEADLAMP relay.
High Beam Indicator Malfunction
Ignition ON, with a scan tool perform the Display Test for the instrument panel cluster (IPC) and observe the high beam indicator.
If the high beam indicator illuminates during the test, replace the BCM.
If the high beam indicator does not illuminate during the test or remains illuminated at all times, replace the IPC.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Bulb Replacement (High Beam) (Service and Repair)
* Headlamp Switch Replacement (Service and Repair)
* Headlamp Aiming (Procedures)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, programming, and setup