The HDM and high beam relay receive battery voltage directly from the battery. The BCM supplies a 100% duty cycle PWM ground signal to the HDM for automatic low beam headlamp control and normal low beam headlamp operation. The BCM also supplies ground to the high beam relay coil for high beam headlamp 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 headlamps and activate the high beam headlamps. With the headlamps in the low beam position, the high beams may be momentarily turned on or flashed by activating the FTP portion of the switch.

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

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. Ignition ON, observe the scan tool Headlamp Switch parameter while cycling the headlamp switch between the Auto and Headlamp ON positions. 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 Headlamp 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 Low Beam Headlamp Malfunction.

3. With the headlamps ON, observe the scan tool High Beam Switch parameter while switching the headlamp dimmer switch between the low and high beam positions. The parameter should cycle between ON and OFF.

⇒	If the parameter does not cycle between the specified values, refer to the Turn Signal/Multifunction Switch Malfunction.

4. With the headlamps ON, observe the headlamps while switching the headlamp dimmer switch between the low and high 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 High Beam Headlamp Malfunction.

5. Ignition ON, pull and release the flash to pass switch. The high beam headlamps should flash ON and OFF.

⇒	If the HI Beam Headlamps do not turn ON and OFF between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.

6. Ignition ON, Headlamps ON, observe the High Beam Indicator while toggling the High Beam Headlamps ON and OFF.

⇒	If the indicator does not turn ON and OFF, refer to High Beam Indicator Malfunction.

Headlamp Switch Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal C.

⇒	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 D 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 D and the ground circuit terminal C. 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 headlamp switch.

Turn Signal/Multifunction 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. Ignition ON, verify the scan tool Flash to Pass parameter is OFF.

⇒	If not the specified value, test the flash to pass switch signal circuit terminal B for a short to ground. If the circuit tests normal, replace the BCM.

5. 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.

6. Install a 3A fused jumper wire between the flash to pass switch 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 flash to pass switch 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.

Low Beam Headlamp Malfunction

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 4 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 control circuit terminal 4 for a short to ground.

5. Disconnect the harness connector at the inoperative low beam headlamp.
6. Test for less than 5.0 ohms between B+ and the ground circuit terminal B.

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

7. 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 ON.

⇒	If the headlamps are always OFF, test the control circuit for a short to ground or an open high resistance.

⇒	If the headlamps are always ON, test the control circuit for short to voltage.

8. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
9. Command the low beam headlamps ON and OFF with the headlamp switch. The test lamp should turn ON and OFF between the commanded states..

⇒	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 BCM.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

10. If all circuits test normal, test or replace the HDM relay.

High Beam Headlamp Malfunction

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.

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 high beam headlamp.
6. Verify that a test lamp illuminates between B+ and the high 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 inoperative high beam headlamp.
8. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the high beam headlamps are activated.

⇒	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, replace the inoperative high beam headlamp.

9. Connect a test lamp between the B+ circuit terminal 30 and the relay control circuit terminal 86.
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 voltage. If the circuit tests normal, replace the 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 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.