With the headlamp switch in the ON position, the headlamp switch headlamp ON signal circuit is grounded through the turn signal/multifunction switch at G200. In response to this input, the instrument panel module (IPM) provides ground to either the headlamp low beam relay control circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay coil has ground. The IPM supplies ground to the relay coil circuits, if the headlamps are necessary. The underhood fuse block supplies battery positive voltage to both relay switch circuits. When the low beam relay coil is energized, current flows through the LT LOW BEAM and the RT LOW BEAM fuses to the low beam headlamps. The low beam headlamps are grounded at G104. When the headlamp high beam relay coil is energized, current flows through the LT HI BEAM and the RT HI BEAM fuses to the high beam headlamps. The high beam headlamps are also grounded at G104. With the headlamp dimmer switch in the high beam position the IPM sends a message via serial data to the instrument panel cluster (IPC) requesting the IPC to illuminate the high beam indicator.

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. Ignition ON, observe the scan tool Headlamp Switch parameter while turning the headlamp switch ON and OFF. The parameter should change between On and Off.

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

2. Observe the scan tool Headlamp/Park Lamp Off Switch parameter while turning the headlamp switch from the PARK and HEAD positions to the OFF position. The parameter change between On and Off.

⇒	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 Headlamp 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 Headlamp Switch Malfunction.

Headlamp Switch Malfunction

1. Ignition OFF, disconnect the X3 and X4 harness connectors at the turn signal/multifunction switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal K.

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

3. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal B.

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

4. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal D.

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

5. Ignition ON, verify the scan tool Headlamp Switch parameter is Off.

⇒	If not the specified value, test the signal circuits at terminal N and terminal L for shorts to ground. If the circuits test normal, replace the IPM.

6. Verify the scan tool Flash to Pass switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the IPM.

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

⇒	If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the IPM.

8. Install a 3A fused jumper wire between the signal circuit terminal N and ground. Verify the scan tool Headlamp 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 IPM.

9. Install a 3A fused jumper wire between the signal circuit terminal L and ground. Verify the scan tool Headlamp 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 IPM.

10. Install a 3A fused jumper wire between the signal circuit terminal A 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 IPM.

11. Install a 3A fused jumper wire between the signal circuit terminal E 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 IPM.

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

Headlamps Malfunction - Low Beam

1. Ignition OFF, disconnect the low beam relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal R25 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 R24 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 R25 for a short to ground. If the circuit tests normal, test or replace the low beam relay.

4. Verify that a test lamp illuminates between the B+ circuit terminal R26 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 inoperative low beam headlamp.
6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

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

7. Connect the harness connector at the inoperative low beam headlamp.
8. Connect a 40A fused jumper wire between the B+ circuit terminal R24 and the control circuit terminal R25. Verify the low beam headlamps are activated.

⇒	If the low beam headlamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative low beam headlamp.

9. Connect a test lamp between the B+ circuit terminal R26 and the control circuit terminal R23.
10. Command the Low Beam Headlamps 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 IPM.

⇒	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 IPM.

11. If all circuits test normal, test or replace the low beam relay.

Headlamps Malfunction - High Beam (Standard)

1. Ignition OFF, disconnect the high beam relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal R29 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 R28 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 R29 for a short to ground. If the circuit tests normal, test or replace the high beam relay.

4. Verify that a test lamp illuminates between the B+ circuit terminal R30 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 inoperative high beam headlamp.
6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

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

7. Connect the harness connector at the inoperative high beam headlamp.
8. Connect a 20A fused jumper wire between the B+ circuit terminal R28 and the control circuit terminal R29. Verify the high beam headlamps are activated.

⇒	If the high beam headlamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative high beam headlamp.

9. Connect a test lamp between the B+ circuit terminal R30 and the control circuit terminal R27.
10. Command the High Beam Headlamps 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 IPM.

⇒	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 IPM.

11. If all circuits test normal, test or replace the high beam relay.

Headlamps Malfunction - High Beam (Intellibeam)

1. Ignition ON, activate the intellibeam feature and observe the intellibeam indicator located on the inside rearview mirror (ISRVM). The indicator should flash 1 time to indicate the system has been activated.

⇒	If the indicator flashes more than 3 times, replace the ISRVM.

2. Ignition OFF, disconnect the harness connector at the inside rearview mirror (ISRVM).
3. Connect a test lamp between B+ and the relay control circuit terminal 3.
4. Command the High Beam Headlamps 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 IPM.

⇒	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 IPM.

5. Connect a test lamp between B+ and the control circuit terminal 4.
6. Ignition ON, verify the test lamp illuminates with the sunload sensor covered and the headlamp switch in the AUTO position.

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

⇒	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 IPM.

7. Ignition OFF, disconnect the harness connector at the automatic headlamp dimming relay.
8. 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.

9. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal 85 and ground.

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

10. 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.

11. Disconnect the harness connector at the inoperative high beam headlamp.
12. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

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

13. Connect the harness connector at the inoperative high beam headlamp.
14. 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 illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the inoperative high beam headlamp.

⇒	If the high beam headlamps illuminate, test the signal circuit terminal 86 for a short to voltage, short to ground or an open/high resistance. If the circuit tests normal, replace the ISRVM.

15. If all circuits test normal, test or replace the automatic headlamp dimming relay.

High Beam Indicator Malfunction (Standard)

Ignition ON, with a scan tool perform the Display Test for the instrument panel cluster (IPC) and observe the high beam indicator.

High Beam Indicator Malfunction (Intellibeam)

1. Ignition ON, with a scan tool perform the Display Test for the instrument panel cluster (IPC) and observe the high beam indicator. The high beam indicator should illuminate during the test and then turn OFF.

⇒	If the high beam indicator does not illuminate or remains illuminated at all times, replace the IPC.

2. Ignition ON, place the headlamp dimmer switch in the high beam position and observe the high beam indicator. The indicator should illuminate.

⇒	If the high beam indicator does not illuminate , replace the IPM.

3. Ignition OFF, disconnect the harness connector at the inside rearview mirror (ISRVM).
4. Test the control circuit terminal 1 for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the ISRVM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.