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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

With the headlamp switch in the ON position, the headlamp switch headlamp ON signal circuit is grounded through the headlamp switch. In response to this input, the body control module (BCM) provides ground to either the headlamp low beam relay control circuit or the headlamp high beam relay control circuit. The position of the turn signal/multifunction switch determines which relay coil is supplied with ground. The BCM supplies ground to the relay coil circuits, if the headlamps are necessary. The underhood fuse block supplies battery voltage to the relay coil and switch circuits. The low beam headlamps operate when the BCM grounds the relay coil control circuit to the relay coil of the low beam relay. This energizes the low beam relay causing the switch contacts to close. With the switch contacts closed, battery voltage is applied to the LT LO and RT LO beam fuses through to the left and right low beam headlamps. When the headlamp high beam relay coil is energized, current flows through the LT HI and the RT HI beam fuses to the high beam headlamps. With the turn signal/multifunction switch in the high beam position the BCM sends a serial data message to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator.

Reference Information
Schematic Reference

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

Programming and Relearning (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, observe the scan tool Headlamp 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 Auto Help. Disable Sw. 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 Flash to Pass 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 Low Beams ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when commanded.

• If the low beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - Low Beam.

6. Command the High Beams ON and OFF with a scan tool. The low 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.

7. Ignition ON, 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 is always ON or OFF, replace the instrument cluster.

Circuit/System Testing

Headlamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 8.

• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Ignition ON, park lamps ON, verify the scan tool Headlamp Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 1 for short to ground. If the circuit tests normal, replace the BCM.

4. Verify the scan tool Auto Help. Disable Sw. parameter is Inactive.

• If not the specified value, test the signal circuit terminal 3 for short to ground. If the circuit tests normal, replace the BCM.

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 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 an open/high resistance. If the circuit tests normal, replace the BCM.

6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Auto Help. Disable Sw. 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 BCM.

7. If all circuits test normal, test or replace the headlamp switch.

Turn Signal/Multifunction Switch Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the turn signal/multifunction switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 8.

• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Verify the scan tool Flash to Pass Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 10 for a short to ground. If the circuit tests normal, replace the BCM.

4. Verify the scan tool High Beam Select Switch parameter is Inactive.

• If not the specified value, test the signal circuit terminal 7 for a short to ground. If the circuit tests normal, replace the BCM.

5. Install a 3 A fused jumper wire between the signal circuit terminal 10 and ground. Verify the scan tool Flash to Pass 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 BCM.

6. Install a 3 A fused jumper wire between the signal circuit terminal 7 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 BCM.

7. If all circuits test normal, test or replace the turn signal/multifunction switch.

Headlamps Malfunction - Low Beam
1. Ignition OFF, disconnect the headlamp low beam 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 85 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. 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 an open/high resistance.

5. Disconnect the harness connector at the appropriate headlamp - low beam.
6. Test for less than 5 ohm between the headlamp - low beam ground circuit terminal listed below and ground:

* RPO WDA and RPO X88 - terminal A
* RPO Z 88 - terminal B

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the headlamp - low beam.
8. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the headlamp - low beam is activated.

• If the headlamp - low beam does not activate and the jumper wire fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the headlamp - low beam.
• If the headlamp - low beam does not activate and the jumper wire fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the headlamp - low beam.

9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the Low 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 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 headlamp low beam relay.

Headlamps Malfunction - High Beam
1. Ignition OFF, disconnect the headlamp high beam 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 85 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. 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 an open/high resistance.

5. Disconnect the harness connector at the appropriate headlamp - high beam.
6. Test for less than 5 ohm between the headlamp ground circuit terminal listed below and ground:

* RPO TVD/W49
* RPO W49 and RPO Z88 - Terminal 1
* RPO WDA - Terminal 3
* RPO Z88 - Terminal I
* Without RPO TVD/W49 - Terminal A

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the headlamp - high beam.
8. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the headlamp - high beam is activated.

• If the headlamp - high beam does not activate and the jumper wire fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the headlamp - high beam.
• If the headlamp - high beam does not activate and the jumper wire fuse is open, test the control circuit for short to ground. If the circuit tests normal, test or replace the headlamp - high beam.

9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. 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 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 headlamps high beam relay.

High Intensity Discharge (HID) Lamp Malfunction
1. Ignition OFF, disconnect the headlamp low beam 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 85 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. 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 an open/high resistance.

5. Disconnect the harness connector at the appropriate headlamp.
6. Test for less than 5 ohm between the headlamp ground circuit terminal 6 and ground

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the headlamp.
8. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the headlamp is activated.

• If the headlamp does not activate and the jumper fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the headlamp.
• If the headlamp does not activate and the jumper fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the headlamp.

9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the Low 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 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 headlamp low beam relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Headlamp Switch Replacement (Service and Repair)
* Headlamp Bulb Replacement (Traverse without TVP High Beam) () Headlamp Bulb Replacement (Traverse with TVP Lo Beam) () Headlamp Bulb Replacement (Traverse without TVP Lo Beam) () Headlamp Bulb Replacement (High Beam without T96) (Headlamp Bulb Replacement (High Beam without T96)) Headlamp Bulb Replacement (Low Beam without T96) (Headlamp Bulb Replacement (Low Beam without T96))
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Headlamp Replacement (Traverse with TVP) (Headlamp Replacement (with TVP)) Headlamp Replacement (Acadia) (Headlamp Replacement (with TVP)) Headlamp Replacement (Enclave) (Headlamp Replacement (with TVP))
* Relay Replacement (Attached to Wire Harness) (Service and Repair)
* Control Module References (Programming and Relearning) for BCM or IPC replacement, setup and programming

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