Buick Regal: DTC B256C or B256D

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 B256C 00

Left Headlamp High Beam Control Module Incorrect Vehicle Identification Number

DTC B256D 00

Right Headlamp High Beam Control Module Incorrect Vehicle Identification Number

Circuit/System Description

The left and right headlamp assemblies each contain a K189 Headlamp/Cornering Lamp Control Module. Both K189 Headlamp/Cornering Lamp Control Modules store the 10 - 17 digits of the vehicles identification number to memory. The K26 Headlamp Control Module compares the vehicles VIN to the 10 - 17 digits of the VIN stored in both K189 Headlamp/Cornering Lamp Control Modules. If either of the VIN's stored do not match, the K26 Headlamp Control Module will set either DTC B256C or B256D depending on what K189 Headlamp/Cornering Lamp Control Modules VIN stored does not match. The driver will be notified with an "Advanced Front Lighting System Fault" message displayed on the driver information center.

Conditions for Running the DTC

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

Conditions for Setting the DTC

DTC B256C 00

The K26 Headlamp Control Module detects and invalid VIN in the K189L Headlamp/Cornering Lamp Control Module - Left.

DTC B256D 00

The K26 Headlamp Control Module detects and invalid VIN in the K189R Headlamp/Cornering Lamp Control Module - Right.

Actions Taken When the DTC Sets

• The high beam headlamps are inoperative.
• The driver information center will display "Advanced Front Lighting System Fault."

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.

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

1. Ignition ON.

2. Verify no other DTC's are set.

• If any other DTC's are set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• Go to next step: If no other DTCs are set

3. Refer to Circuit/System Testing.

Circuit/System Testing

1. Ignition ON.

2. Verify DTC B256C or B256D is not set.

• If DTC B256C or B256D is set

1. Program the K26 Headlamp Control Module.
2. Verify DTC B256C or B256D is not set.

• If DTC B256C or B256D is set

Replace the appropriate K189 Headlamp/Cornering Lamp Control Module.

• Go to next step: If DTC B256C or B256D is not set

Go to next step: All OK.

• Go to next step: If DTC B256C or B256D is not set

3. All OK

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for Headlamp Control Module or Headlamp/Cornering Lamp Control Module replacement, programming, and setup.

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