Buick Regal: Headlamp Leveling Malfunction (Automatic)

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

Automatic Headlamp Leveling (without Electronic Suspension Control)

The automatic headlamp leveling system automatically maintains the vertical alignment of the headlamps when the vehicle load and driving conditions change. The vehicle is equipped with suspension height sensors located on the left front and left rear suspensions. Each sensor receives a 5 V reference, signal, and low reference circuits from the headlamp control module. The headlamp control module receives inputs from the front and rear suspension height sensors to determine vehicle pitch. The headlamp control module calculates the difference in vehicle pitch and sends a serial data message to both headlamp leveling control modules located in each headlamp assembly. The headlamp leveling control modules responds by driving their respective headlamp leveling actuators to the position commanded by the headlamp control module.

Automatic Headlamp Leveling (with Electronic Suspension Control)

The front and rear vertical suspension acceleration sensors provide the suspension control module with suspension position information. Each sensor receives a 5 V reference, signal, and low reference circuits from the suspension control module. The vertical suspension acceleration sensors are connected to each control arm of the front and rear suspensions. As the vehicle travels, the suspension compresses and rebounds moving the vertical suspension acceleration sensors. This causes the signal output of the sensor to change. The suspension control module compares the information from all four vertical suspension acceleration sensors and adjusts the suspension as needed. The suspension control module communicates the suspension positions with the headlamp control module via serial data. The headlamp control module uses the suspension position sensor information received from the suspension control module to calculate the difference in vehicle pitch and sends a serial data message to both headlamp leveling control modules located in each headlamp assembly. The headlamp leveling control modules responds by driving their respective headlamp leveling actuators to the position commanded by the headlamp control module.

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) 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.

Special Tools

J-38522 Variable Signal Generator

For equivalent regional tools, refer to Special Tools.

Circuit/System Verification

1. Ignition ON.

2. Verify the low beam headlamps turn ON and OFF while commanding the low beam headlamps ON and OFF with the headlamp switch.

• If the low beam headlamps do not turn ON and OFF

Refer to Headlamps Malfunction

• Go to next step: If the low beam headlamps turn ON and OFF

3. Verify the scan tool Front Leveling Position Sensor Signal parameter is between 5 % and 90 %.

• If the parameter is not between 5 % and 90 %

Refer to Circuit/System Testing - Headlamp Leveling Sensor Malfunction.

• Go to next step: If the parameter is between 5 % and 90 %

4. Verify the scan tool Rear Leveling Position Sensor Signal parameter is between 5 % and 90 %.

• If the parameter is not between 5 % and 90 %

Refer to Circuit/System Testing - Headlamp Leveling Sensor Malfunction.

• Go to next step: If the parameter is between 5 % and 90 %

5. Verify the left headlamp operates to the UP and DOWN positions when commanding the Left Headlamp Vertical Motor UP and DOWN with a scan tool.

• If the left headlamp does not operate UP and DOWN

Refer to Circuit/System Testing - Headlamp Leveling Actuator Malfunction

• Go to next step: If the left headlamp operates UP and DOWN

6. Verify the right headlamp operates to the UP and DOWN positions when commanding the Right Headlamp Vertical Motor UP and DOWN with a scan tool.

• If the right headlamp does not operate UP and DOWN

Refer to Circuit/System Testing - Headlamp Leveling Actuator Malfunction

• Go to next step: If the right headlamp operates UP and DOWN

7. All OK.

Circuit/System Testing

Headlamp Leveling Actuator Malfunction

1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly.

2. Test for less than 15 Ω between the ground circuit terminal 2 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

3. Ignition ON.

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

• If the test lamp does not illuminate

1. Ignition OFF, disconnect the X5 harness connector 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 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 X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

5. Test or replace the appropriate K26L/R Headlamp Control Module located within Headlamp Assembly.

6. Ignition ON.

7. Verify the appropriate headlamp operates to the UP and DOWN positions when commanding the appropriate Headlamp Vertical Motor UP and DOWN with a scan tool.

• If the headlamp does not operate UP and DOWN

Test or replace the E13 Headlamp Assembly.

• Go to next step: If the headlamp operates UP and DOWN

8. All OK.

Headlamp Leveling Sensor Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate B51 Suspension Height Sensor, ignition ON.

2. Verify a test lamp illuminates between the low reference circuit terminal 2 and B+.

• If the test lamp does not illuminate

1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K26 Headlamp Control Module.

• Go to next step: If the test lamp illuminates

3. Ignition ON.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 1 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
2. Test for infinite resistance between the 5 V reference 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 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K26 Headlamp Control Module.

• If greater than 5.2 V

1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K26 Headlamp Control Module.

• Go to next step: If between 4.8 - 5.2 V

5. Verify the appropriate scan tool Leveling Position Sensor Signal parameter is less than 1 mm.

• If 1 mm or greater

1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 3 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K26 Headlamp Control Module.

• Go to next step: If less than 1 mm

6. Ignition OFF.

7. Connect the red lead of the J-38522 Variable Signal Generator to the signal circuit terminal 3 and the black lead of the J-38522 Variable Signal Generator to the low reference circuit terminal 2.

8. Adjust the J-38522 Variable Signal Generator to the settings listed below:

• Signal control to 5 V
• Frequency control to 250 Hz
• Duty cycle control to 60%

9. Ignition ON, verify the appropriate scan tool Leveling Position Sensor parameter is 11 mm.

• If not 11 mm

1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
2. Test for infinite resistance between the signal 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K26 Headlamp Control Module.

• Go to next step: If 11 mm

10. Test or replace the appropriate B51 Suspension Height Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Headlamp Replacement
• Headlamp Control Module Replacement
• Headlamp LED Driver Module Replacement
• Front Suspension Automatic Forward Lighting Position Sensor Replacement
• Rear Suspension Automatic Forward Lighting Leveling Position Sensor Replacement
• Engine Wiring Harness Fuse Block Bracket Replacement
• Control Module References for Headlamp Control Module replacement, programming, and setup

INTERIOR ACCENT LIGHTING MALFUNCTION

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. Interior Accent Lighting Malfunction

Circuit/System Description

The body control module (BCM) supplies battery voltage to accent lighting lamps via the accent lamp control circuit. When a door is opened the BCM applies battery voltage to the accent lamp control circuit illuminating all of the accent lighting. The accent lighting will remain illuminated until all doors are closed and the ignition is OFF. The accent lighting remains illuminated with the ignition ON.

Reference Information

Schematic Reference

Interior Lights Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Interior 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, scan tool disconnected, all doors closed, all accessories OFF, open and close drivers door, disconnect the harness connector at the component with the inoperative LED backlighting. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the appropriate ground circuit terminal 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. Connect a test lamp between the appropriate control circuit terminal and ground, ignition ON.

4. Verify the test lamp turns ON and OFF when commanding the Accent Lighting 1 ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the appropriate harness connector below at the K9 Body Control Module.
   • X7
   • X1
2. Test for infinite resistance between the control 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 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 K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the appropriate harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

5. Test or replace the appropriate accent lamp.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Front Side Door Map Pocket Illumination Lamp Replacement
• Front Side Door Inside Handle Illumination Lamp Replacement
• Rear Side Door Inside Handle Illumination Lamp Replacement
• Control Module References for BCM replacement, programming, and setup

READ NEXT: