Buick Regal Owners & Service Manuals

Buick Regal: DTC B25F6 or B25F7

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 B25F6 00

Left Headlamp Cooling Fan Circuit Malfunction

DTC B25F7 00

Right Headlamp Cooling Fan Circuit Malfunction

Circuit/System Description

The temperature of each headlamp assembly is measured by three temperature sensors. Each headlamp assembly includes a temperature sensor for the cornering lamp LEDs, low beam LEDs, and high beam LEDs. In the case that either headlamp assembly overheats, the low beam control module activates the appropriate cooling fan.

Conditions for Running the DTC

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

Conditions for Setting the DTC

DTC B25F6 00

The headlamp control module detects a malfunction on the left headlamp cooling fan circuit.

DTC B25F7 00

The headlamp control module detects a malfunction on the right headlamp cooling fan circuit.

Actions Taken When the DTC Sets

  • 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.

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

1. Ignition OFF, remove the appropriate K135 Headlamp Low Beam Control Module.

2. Install a jumper wire between the ground circuit terminal 29 at the K135 Headlamp Low Beam Control Module harness connector and the ground circuit terminal 1 at the appropriate harness connector listed below.

  • X110 - left headlamp assembly
  • X120 - right headlamp assembly

3. Install a 10 A fused jumper wire between the signal circuit terminal 30 at the K135 Headlamp Low Beam Control Module harness connector and the B+ circuit terminal 3 at the appropriate harness connector listed below.

  • X110 - left headlamp assembly
  • X120 - right headlamp assembly

4. Verify the appropriate G46 Cooling Fan - Headlamp turns ON.

  • If the G46 Cooling Fan - Headlamp does not turn ON

Replace the E13 Headlamp Assembly.

  • Go to next step: If the G46 Cooling Fan - Headlamp turns ON

5. Replace the K135 Headlamp Low Beam Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

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

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