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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 and panel dimmer switch. In response to this input, the body control module (BCM) provides ground to either the high intensity discharge (HID) headlamp control circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay coil is supplied with ground. The underhood fuse block supplies battery voltage to the relay coil and switch circuits. The HID headlamps operate when the BCM grounds the HID headlamp relay control circuit to the HID headlamp relay coil. This energizes the HID headlamp relay coil causing the switch contacts to close. With the switch contacts closed, battery voltage is applied to the left and right HID fuses through to the left and right HID headlamps. When the headlamp high beam relay coil is energized, current flows through the left and right HIGH BEAM fuses to the high beam headlamps. With the headlamp dimmer switch in the high beam position the BCM sends a serial data message to the instrument cluster requesting to illuminate the high beam indicator.

Reference Information
Schematic Reference

Headlights Schematics (Headlights Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
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

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, observe the scan tool Headlamp On Switch parameter while turning the headlamp switch ON and OFF. The reading should toggle between Active and Inactive.

• If the reading does not change between the commanded states, refer to Headlamp Switch Malfunction.

2. Observe the scan tool Automatic Headlamp Disable Switch parameter while applying and releasing the automatic lamp control disable switch. The reading should toggle between Active and Inactive.

• If the reading does not change between the commanded states, refer to Headlamp Switch Malfunction.

3. Observe the scan tool Headlamps Flash Switch parameter while applying and releasing the flash to pass switch. The reading should toggle between Active and Inactive.

• If the reading 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 reading should toggle between Active and Inactive.

• If the reading does not change between the commanded states, refer to Turn Signal/Multifunction Switch Malfunction.

5. Command the Headlamp Low Beam Command 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 Beams.

6. Command the Dedicated Daytime Running Lamp ON and OFF with a scan tool. The daytime running lamp should turn ON and OFF when commanded.

• If the daytime running lamp does not turn ON and OFF when commanded, refer to Headlamps Malfunction - Daytime Running Lamps.

7. Command the High Beam Headlamps ON and OFF with a scan tool. The high 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.

8. Command the All Indicators Test ON and OFF with a scan tool. The lights on indicator and high beam indicator should turn ON and OFF when changing between the commanded states.

• If the lights on indicator and high beam indicator illuminate during the test, replace the K9 BCM.
• If the lights on indicator and high beam indicator do not illuminate during the test or remain illuminated at all times, replace the P16 instrument cluster.

Circuit/System Testing

Warning

The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:

* Never open the high intensity discharge system ballast or the arc tube assembly starter.
* Never probe between the high intensity discharge system ballast output connector and the arc tube assembly.

Headlamp Switch Malfunction
1. Ignition OFF, disconnect the harness connectors at the S30 headlamp switch.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal 6 and ground.

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

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

• If not the specified value, test the signal circuit terminal 4 for short to ground. If the circuit tests normal, replace the K9 BCM.

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

• If not the specified value, test the signal circuit terminal 5 for short to ground. If the circuit tests normal, replace the K9 BCM.

5. Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Headlamp 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 BCM.

6. Install a 3 A fused jumper wire between the signal circuit terminal 5 and ground. Verify the scan tool Automatic Headlamp 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 BCM.

7. If all circuits test normal, test or replace the S30 headlamp switch.

Turn Signal/Multifunction Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S78 turn signal/multifunction switch.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal 3 and ground.

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

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

• If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 BCM.

4. Verify the scan tool High Beam Select 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 BCM.

5. Install a 3 A fused jumper wire between the signal circuit terminal 4 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 BCM.

6. Install a 3 A fused jumper wire between the signal circuit terminal 2 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 K9 BCM.

7. If all circuits test normal, test or replace the S78 turn signal/multifunction switch.

Headlamps Malfunction - Low Beam
1. Ignition OFF, disconnect the KR49 low beam 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 86 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 T7 headlamp.
6. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohm between the ground circuit terminal A and ground.

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

7. Connect the harness connector at the T7 headlamp.
8. Connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the T7 headlamps are activated.

• If the T7 headlamps do not activate and the circuit fuse is good, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the T7 headlamp ballast.
• If the T7 headlamps do not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the T7 headlamp ballast.

9. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
10. Command the Headlamp Low Beam Command 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 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 K9 BCM.

11. If all circuits test normal, test or replace the KR49 low beam headlamp relay.

Headlamps Malfunction - Daytime Running Lamps
1. Ignition OFF, disconnect the harness connector at the appropriate E4 daytime running lamp.
2. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohm between the ground circuit terminal 2 and ground.

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

3. Connect a test lamp between the signal circuit terminal 1 and ground.
4. Command the Dedicated Daytime Running Lamp 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 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 BCM.

5. If all circuits test normal, replace the E4 daytime running lamp.

Headlamps Malfunction - High Beam
1. Ignition OFF, disconnect the X2 harness connector at X50A underhood fuse block.
2. Connect a test lamp between the control circuit terminal 31 and B+.
3. 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 K9 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 K9 BCM.

4. Ignition OFF, connect the X2 harness connector at the X50A underhood fuse block. Disconnect the harness connector at the appropriate M28 High Beam Solenoid Actuator.
5. Test for less than 5 ohm between the ground circuit terminal A and ground.

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

6. Connect a test lamp between the control circuit terminal C and ground.
7. 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 voltage. If the circuit tests normal, replace the X50A underhood fuse block.
• If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the X50A underhood fuse block.
• If the test lamp is always off and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test of replace the M28 High Beam Solenoid Actuator.

8. If all circuits test normal, test or replace the X50A underhood fuse block.

Repair Instructions

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

* Accessory Wiring Junction Block Retainer Replacement (Removal and Replacement)
* Daytime Running Lamp Replacement (Daytime Running Lamp Replacement)
* Daytime Running Lamp Bulb Replacement (Daytime Running Lamp Bulb Replacement)
* Headlamp Replacement (Headlamp Replacement)
* Headlamp Ballast Replacement (Headlamp Ballast Replacement)
* Headlamp Bulb Replacement (Service and Repair)
* Headlamp, Instrument Panel Lamp Dimmer, and Fog Lamp Switch Replacement (Service and Repair)
* Relay Replacement (Removal and Replacement)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Control Module References (Programming and Relearning) for BCM or instrument cluster replacement, setup, and programming

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