Buick Regal: DTC B25F4 or B25F5

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 B25F4 00

Left Headlamp High Beam Control Module Malfunction

DTC B25F4 3A

Left Headlamp High Beam Control Module Incorrect Component Installed

DTC B25F4 42

Left Headlamp High Beam Control Module Calibration Not Programmed

DTC B25F5 00

Right Headlamp High Beam Control Module Malfunction

DTC B25F5 3A

Right Headlamp High Beam Control Module Incorrect Component Installed

DTC B25F5 42

Right Headlamp High Beam Control Module Calibration Not Programmed

Circuit/System Description

The high beam and flash to pass functions are contained within the turn signal/multifunction switch. The body control module (BCM) provides the turn signal/multifunction switch with two signal circuits, the high beam signal circuit and the flash to pass signal circuit. When the low beam headlamps are ON and the turn signal/multifunction switch is placed in the high beam position, ground is applied to the BCM through the high beam signal circuit. The BCM responds to the high beam request by sending a message via high speed bus to the headlamp control module. The headlamp control module then communicates via private CAN bus with the left and right high beam control modules to illuminate the high beam LEDs.

The part numbers for the left and right high beam control module are stored in the respective left and right high beam control modules. The headlamp control module compares the part numbers. If the part numbers do not match, DTC B25F4 3A or B25F5 3A will set.

Conditions for Running the DTC

• Battery voltage must be between 9 - 16 V.
• High beam headlamps ON.

Conditions for Setting the DTC

DTC B25F4 00 and B25F4 42

The headlamp control module detects that an internal malfunction has occurred in the left high beam control module.

DTC B25F4 3A

The headlamp control module detects that an incorrect component was installed.

DTC B25F5 00 and B25F4 42

The headlamp control module detects that an internal malfunction has occurred in the right high beam control module.

DTC B25F5 3A

The headlamp control module detects that an incorrect component was installed.

Actions Taken When the DTC Sets

• One or more high beam LEDs are inoperative.
• The driver information center will display Advanced Front Lighting System Fault and Head Light Leveling Failure.

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 are serviceable within the headlamp assemblies so complete headlamp assembly replacement is necessary. The appropriate K135 Headlamp Low Beam Control Module, K191 Headlamp High Beam Control Module, and K166 Multifunction LED Control Module may be reused when replacing the headlamp assembly.

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

DTC B25F4 00 or B25F5 00

1. Ignition ON.

2. Verify DTC B25F4 00 or B25F5 00 is not set.

• If DTC B25F4 00 or B25F5 00 is set

Replace the appropriate K191 Headlamp High Beam Control Module.

• Go to next step: If DTC B25F4 00 or B25F5 00 is not set

3. All OK

DTC B25F4 42 or B25F5 42

1. Ignition ON.

2. Verify DTC B25F4 42 or B25F5 42 is not set.

• If DTC B25F4 42 or B25F5 42 is set

1. Program the K26 Headlamp Control Module.
2. Verify the DTC does not set.
   • If the DTC sets, replace the appropriate K191 Headlamp High Beam Control Module.
   • Go to next step: If the DTC does not set
3. All OK.

• Go to next step: If DTC B25F4 42 or B25F5 42 is not set

3. All OK

DTC B25F4 3A or B25F5 3A

1. Ignition ON.

2. Verify DTC B25F4 3A or B25F5 3A is not set.

• If DTC B25F4 3A or B25F5 3A is set

1. Verify the appropriate K191 Headlamp High Beam Control Module part number is installed on the vehicle.
   • If the incorrect K191 Headlamp High Beam Control Module is installed, replace the K191 Headlamp High Beam Control Module.
   • Go to next step: If the correct K191 Headlamp High Beam Control Module is installed
2. Program the K26 Headlamp Control Module.
3. Verify the DTC does not set.

• If the DTC sets

1. Replace the appropriate K191 Headlamp High Beam Control Module.
2. Verify the DTC does not set.
   • If the DTC sets, replace the K26 Headlamp Control Module.
   • Go to next step: If the DTC does not set, all OK.

• Go to next step: If the DTC does not set

4. All OK.

• Go to next step: If DTC B25F4 3A or B25F5 3A is not set

3. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

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

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