Buick Regal: DTC B25FC or B25FD

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.

DTC Descriptors

DTC B25FC 00

Left Headlamp Leveling Control Module Malfunction

DTC B25FC 3A

Left Headlamp Leveling Control Module Incorrect Component Installed

DTC B25FD 00

Right Headlamp Leveling Control Module Malfunction

DTC B25FD 3A

Right Headlamp Leveling Control Module Incorrect Component Installed

Diagnostic Fault Information

1. Headlamp Leveling Malfunction

Circuit/System Description

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.

Conditions for Running the DTC

• Battery voltage must be between 9 - 16 V.
• Engine RUNNING.
• Low beam headlamps ON.

Conditions for Setting the DTC

DTC B25FC 00

The headlamp control module detects an internal malfunction with the headlamp leveling control module - left.

DTC B25FC 3A

The headlamp control module detects an incorrect component for the left headlamp leveling system has been installed.

DTC B25FD 00

The headlamp control module detects an internal malfunction with the headlamp leveling control module - right.

DTC B25FD 3A

The headlamp control module detects an incorrect component for the right headlamp leveling system has been installed.

Actions Taken When the DTC Sets

• Advanced front lighting and headlamp leveling are disabled.
• The driver information center will display "Advanced Front Lighting System Fault" and "Headlamp Leveling Malfunction".

Conditions for Clearing the DTC

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Diagnostic Aids

No parts within the headlamp assemblies are serviceable so complete headlamp assembly replacement is necessary. When replacing a headlamp assembly, the following control modules located on each headlamp assembly should be reused.

• K189L Headlamp/Cornering Lamp Control Module - Left
• K189R Headlamp/Cornering Lamp Control Module - Right
• K28L Headlamp Leveling Control Module - Left
• K28R Headlamp Leveling Control Module - Right

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 Verification

DTC B25FC 00 and B25FD 00

1. Ignition ON.

2. Verify DTC B25FC 00 or B25FD 00 is not set.

• If DTC B25FC 00 or B25FD 00 is set

Replace the appropriate E13 Headlamp Assembly.

• Go to next step: If DTC B25FC 00 or B25FD 00 is not set

3. All OK

DTC B25FC 3A and B25FD 3A

1. Ignition ON.

2. Verify DTC B25FC 3A or B25FD 3A is not set.

• If DTC B25FC 3A or B25FD 3A is set

1. Verify the appropriate E13 Headlamp Assembly part number is installed on the vehicle.
   • If an incorrect E13 Headlamp Assembly is installed

     Replace the E13 Headlamp Assembly.

   • Go to next step: If the correct E13 Headlamp Assembly is installed
2. Program the K26 Headlamp Control Module.
3. Verify DTC B25FC 3A or B25FD 3A is not set.

• If DTC B25FC 3A or B25FD 3A is set

1. Replace the E13 Headlamp Assembly.
2. Verify DTC B25FC 3A or B25FD 3A is not set.
   • If DTC B25FC 3A or B25FD 3A is set

     Replace the K26 Headlamp Control Module.

   • Go to next step: If DTC B25FC 3A or B25FD 3A is not set

     Go to next step: All OK.

• Go to next step: If DTC B25FC 3A or B25FD 3A is not set

3. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Headlamp Replacement
• Control Module References for Headlamp Control Module replacement, programming, and setup

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