Volt

Headlamps Malfunction

For headlamp operation, the body control module (BCM) monitors three signal circuits from the indicator/multifunction switch. When the indicator/multifunction switch is in the AUTO position, the three signal circuits are open and the BCM relies on the ambient light sensor input to turn the headlamps and daytime running lamps (DRL) ON and OFF. When the indicator/multifunction switch is placed in the OFF position, the indicator/multifunction switch headlamps OFF signal circuit is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the indicator/multifunction switch in the PARK lamps position, the indicator/multifunction switch sidelights ON signal circuit is grounded, indicating that the sidelights have been requested. When the indicator/multifunction switch is in the HEADLAMP position, both the indicator/multifunction switch sidelights ON signal circuit and the indicator/multifunction switch headlamps ON signal circuit are grounded. The BCM responds by commanding the sidelights and headlamps ON.

The main beam and flash to pass functions are contained within the indicator/multifunction switch. The BCM provides the indicator/multifunction switch with two signal circuits, the main beam signal circuit and the flash to pass signal circuit. When the dipped beam headlamps are ON and the indicator/multifunction switch is placed in the main beam position, ground is applied to the BCM through the main beam signal circuit. The BCM responds to the main beam request by applying ground to the main beam relay control circuit which energises the main beam relay. With the main beam relay energised, the switch contacts close allowing battery voltage to flow through the main beam fuses to the main beam control circuits illuminating the main beam headlamps.

When the indicator/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 main beam relay control circuit which energises the main beam relay illuminating the main beams for a brief moment or until the flash to pass switch is released.

Schematic Reference

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle in Service Mode, observe the scan tool Headlamps On Switch parameter while turning the dipped beam headlamps ON and OFF with the indicator/multifunction switch. The parameter should change between Active and Inactive.

⇒	If the parameter does not change between the commanded states, refer to Indicator/Multifunction 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 Indicator/Multifunction Switch Malfunction.

3. Observe the scan tool Main Beam Select Switch parameter while applying and releasing the main beam select switch. The parameter should change between Active and Inactive.

⇒	If the parameter does not change between the commanded states, refer to Indicator/Multifunction Switch Malfunction.

4. 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 Indicator/Multifunction Switch Malfunction.

5. Command the Left Headlamp Dipped Beam ON and OFF with a scan tool. The left dipped beam headlamp should turn ON and OFF when commanded.

⇒	If the left dipped beam headlamp does not turn ON and OFF when commanded, refer to Headlamps Malfunction - Dipped Beam.

6. Command the Right Headlamp Dipped Beam ON and OFF with a scan tool. The right dipped beam headlamp should turn ON and OFF when commanded.

⇒	If the right dipped beam headlamp does not turn ON and OFF when commanded, refer to Headlamps Malfunction - Dipped Beam.

7. Dipped beam headlamps ON, command the Main Beams ON and OFF with a scan tool. The main beam headlamps should turn ON and OFF when commanded.

⇒	If the main beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - Main Beam.

8. Observe the main beam indicator while applying and releasing the main beam select switch. The main beam indicator should turn ON and OFF when changing between the commanded states.

⇒	If the main beam indicator does not illuminate or remains illuminated at all times, replace the P16 Instrument Cluster.

Indicator/Multifunction Switch Malfunction

1. Vehicle OFF, disconnect the harness connector at the S78 Indicator/Multifunction Switch.
2. Vehicle OFF, scan tool disconnected, all doors closed, all accessories OFF, and wait 2 minutes. Test for less than 10 Ω between the ground circuit terminal 6 and ground.

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

3. Vehicle in Service Mode, verify the scan tool Headlamps On 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 Body Control Module.

4. Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal 9 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.

5. Verify the scan tool Main Beam Select Switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal 11 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.

6. Verify the scan tool Headlamps Flash Switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal 12 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.

7. Install a 3 A fused jumper wire between the signal circuit terminal 2 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 Body Control Module.

8. Install a 3 A fused jumper wire between the signal circuit terminal 9 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 Body Control Module.

9. Install a 3 A fused jumper wire between the signal circuit terminal 11 and ground. Verify the scan tool Main 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 Body Control Module.

10. Install a 3 A fused jumper wire between the signal circuit terminal 12 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 Body Control Module.

11. If all circuits test normal, replace the S78 Indicator/Multifunction Switch.

Headlamps Malfunction - Dipped beam

1. Vehicle OFF, disconnect the X1 harness connector at the K9 Body Control Module.
2. Vehicle in Service Mode, 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.

3. Verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.

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

4. Vehicle OFF, connect the X1 harness connector at the K9 Body Control Module.
5. Disconnect the harness connector at the inoperative headlamp.
6. Vehicle OFF, exterior lamps OFF, test for less than 5 Ω between the ground circuit terminal 5 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 1 and ground.
8. Vehicle in Service Mode, command the appropriate Headlamp Dipped Beam 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 Body Control Module.

⇒	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 Body Control Module.

9. If all circuits test normal, replace the inoperative headlamp.

Headlamps Malfunction - Main beam

1. Vehicle OFF, disconnect the X1 harness connector at the X50A Fuse Block - Under-bonnet.
2. Connect a test lamp between the control circuit terminal 18 and B+.
3. Vehicle in Service Mode, command the Main 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 Body Control Module.

⇒	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 Body Control Module.

4. Vehicle OFF, connect the X2 harness connector at the X50A Fuse Block - Under-bonnet.
5. Disconnect the harness connector at the inoperative headlamp.
6. Vehicle OFF, exterior lamps OFF, test for less than 5 Ω between the ground circuit terminal 4 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. Vehicle in Service Mode, dipped beam headlamps ON, command the Main 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 - Under-bonnet.

⇒	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 - Under-bonnet.

9. If all circuits test normal, replace the inoperative headlamp.

Perform the Diagnostic Repair Verification