Headlamps Malfunction
Headlamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The headlamps may be turned ON in 3 different ways:
* When the headlamp switch is placed in the ON position, for normal operation
* When the headlamp switch is placed in the AUTO position, for automatic lamp control (ALC)
* When the headlamp switch is placed in the AUTO position, with the windshield wipers ON in daylight conditions, after a 6 second delay (including activation of windshield wipers by moisture sensitive wiper system)
With the headlamp switch in the ON position, the headlamp switch headlamp ON signal circuit is grounded through the turn signal/multifunction switch. In response to this input, the instrument panel module 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 instrument panel module 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. 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. With the headlamp dimmer switch in the high beam position the instrument panel module sends a message via serial data 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 (Headlights/Daytime Running Lights (DRL) Schematics)
* Inside Rearview Mirror Schematics (Inside Rearview Mirror 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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
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 turning the headlamp switch ON and OFF. The parameter should change between On and Off when changing between the selected states.
• If the parameter does not change between the commanded states, refer to Turn Signal/Multifunction 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 when changing between the selected states.
• If the parameter does not change between the commanded states, refer to Turn Signal/Multifunction 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 when changing between the selected states.
• 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 when changing between the selected states.
• 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 changing between the commanded states.
• 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 high beam headlamps should turn ON and OFF when changing between the commanded states.
• If the high beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction - High Beam.
7. Ignition ON, with the turn signal/multifunction switch in the neutral position (high beams not ON), apply light through the windshield to the front of the inside rearview mirror. The high beam headlights should dim when the light is detected.
• If the high beam headlights do not dim, refer to Headlamps Malfunction - High Beam (Intellibeam).
8. 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
Turn Signal/Multifunction 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 instrument panel module.
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 instrument panel module.
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 instrument panel module.
8. Install a 3 A 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 instrument panel module.
9. Install a 3 A 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 instrument panel module.
10. Install a 3 A 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 instrument panel module.
11. Install a 3 A 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 instrument panel module.
12. If all circuits test normal, test or replace the turn signal/multifunction switch.
Headlamps Malfunction - Low Beam (T84)
1. Ignition OFF, disconnect the Low Beam Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 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 inoperative headlamp.
6. Test for less than 5 ohm between the headlamp ground circuit terminal 2 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 20 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.
• 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.
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 instrument panel 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 instrument panel module.
11. If all circuits test normal, test or replace the Low Beam Relay.
Headlamps Malfunction - Low Beam (High Intensity Discharge Lamps)
1. Ignition OFF, disconnect the HID Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 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 inoperative headlamp.
6. Test for less than 5 ohm between the headlamp ground circuit terminal 4 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 20 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.
• 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.
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 instrument panel 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 instrument panel module.
11. If all circuits test normal, test or replace the HID Relay.
Headlamps Malfunction - High Beam (Intellibeam)
1. Ignition ON, activate the intellibeam feature and observe the intellibeam indicator located on the inside rearview mirror. The indicator should flash 1 time to indicate the system has been activated.
• If the indicator flashes more than 3 times, replace the inside rearview mirror.
2. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
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 instrument panel 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 instrument panel module.
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 instrument panel 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 instrument panel module.
7. Ignition OFF, disconnect the automatic headlamp dimming relay.
8. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 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 ohm 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 headlamp.
12. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 4 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
13. Connect the harness connector at the headlamp.
14. Connect a 15 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.
• If the headlamp - high 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.
15. Connect a test lamp between the ground circuit terminal 85 and the control circuit terminal 86.
16. Command the Automatic Headlamp Dimming 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 inside rearview mirror.
• 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 inside rearview mirror.
17. If all circuits test normal, test or replace the automatic headlamp dimming relay.
Headlamps Malfunction - High Beam (T84)
1. Ignition OFF, disconnect the High Beam Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 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 inoperative headlamp.
6. Test for less than 5 ohm between the headlamp ground circuit terminal 2 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 - 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.
• If the headlamp - high 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.
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 instrument panel 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 instrument panel module.
11. If all circuits test normal, test or replace the High Beam Relay.
Headlamps Malfunction - High Beam (with High Intensity Discharge Headlamps)
1. Ignition OFF, disconnect the High Beam Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 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 a short to ground or an open/high resistance.
5. Disconnect the harness connector at the inoperative headlamp.
6. Test for less than 5 ohm between the headlamp ground circuit terminal 4 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 - 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.
• If the headlamp - high 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.
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 instrument panel 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 instrument panel module.
11. If all circuits test normal, test or replace the High Beam Relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Bulb Replacement (HID Hi Beam) (Service and Repair)Headlamp Bulb Replacement (HID Lo Beam) (Service and Repair)Headlamp Bulb Replacement (Lo Beam) (Service and Repair)Headlamp Bulb Replacement (Hi Beam) (Service and Repair)
* Headlamp Replacement (Service and Repair)
* Headlamp Ballast Replacement (STS) (Service and Repair)Headlamp Ballast Replacement (STS-V) (Service and Repair)
* Underhood Electrical Center or Junction Block Replacement (Service and Repair)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for instrument panel module, instrument cluster or inside rearview mirror replacement, setup, and programming