Buick Regal: Headlamp Leveling Malfunction (Manual)

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

1. Headlamp Leveling Malfunction

Circuit/System Description

Each headlamp assembly contains a headlamp leveling actuator that is controlled by the headlamp leveling switch. The headlamp leveling switch is supplied with ignition voltage and ground and contains a resistor ladder with 4 positions for adjusting the headlamps up or down. When the headlamp leveling switch is activated to the desired position, voltage from the B+ ignition circuit is pulled down through the resistor ladder and the voltage is applied to the left and right headlamp leveling actuators via the headlamp leveling control circuits. The headlamp leveling actuators are supplied with B+ and ground.

When the headlamp leveling switch is activated, the left and right headlamp leveling actuators respond by moving the headlamps to the desired position.

Diagnostic Aids

For testing purposes, the vehicle battery must be fully charged.

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Testing

1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 7 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Verify a test lamp illuminates between the B+ ignition circuit terminal 6 and ground.

• If the test lamp does not illuminate

1. Ignition OFF, remove the F44UA fuse at the X50A Fuse Block - Underhood.
2. Test for infinite resistance between the B+ ignition circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

5. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S30 Headlamp Switch. It may take up to 2 min for all vehicle systems to power down.

6. Test for less than 15 Ω between the ground circuit terminal 8 and ground.

• If 15 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 15 Ω

7. Ignition ON.

8. Verify a test lamp illuminates between the B+ ignition circuit terminal 4 and ground.

• If the test lamp does not illuminate

1. Ignition OFF, remove the F27UA fuse at the X50A Fuse Block - Underhood.
2. Test for infinite resistance between the B+ circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the B+ circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

9. Ignition OFF, connect the harness connector at the S30 Headlamp Switch.

10. Ignition ON, exterior lights OFF.

11. Test the voltage between the control circuit terminal 8 at the E13 Headlamp Assembly harness connector and ground for each headlamp leveling switch position listed below.

• Headlamp leveling switch position 0 - 10 V - 11 V
• Headlamp leveling switch position 1 - 8.5 V - 9.9 V
• Headlamp leveling switch position 2 - 8 V - 9 V
• Headlamp leveling switch position 3 - 6 V - 7 V
• If less than the specified voltage range for each headlamp leveling switch position

1. Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch.
2. Test for infinite resistance between the control circuit terminal 9 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the S30 Headlamp Switch.

• If greater than the specified voltage range for each headlamp leveling switch position

1. Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch, ignition ON.
2. Test for less than 1 V between the control circuit terminal 9 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the S30 Headlamp Switch.

• Go to next step: If within the specified voltage range for each headlamp leveling switch position

12. Test or replace the E13 Headlamp Assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Headlamp Switch Replacement
• Headlamp Replacement

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