Buick Regal: DTC B25FA or B25FB
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 B25FA 03
Left Headlamp Leveling Control Module Supply Circuit Low Voltage
DTC B25FA 07
Left Headlamp Leveling Control Module Supply Circuit High Voltage
DTC B25FB 03
Right Headlamp Leveling Control Module Supply Circuit Low Voltage
DTC B25FB 07
Right Headlamp Leveling Control Module Supply Circuit High Voltage
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.
- Ignition ON.
- Headlamps ON.
Conditions for Setting the DTC
DTC B25FA 03
The headlamp control module detects a low voltage condition in the headlamp
leveling control module -
left B+ circuit.
DTC B25FA 07
The headlamp control module detects a high voltage condition in the headlamp
leveling control module
- left B+ circuit.
DTC B25FB 03
The headlamp control module detects a low voltage condition in the headlamp
leveling control module -
right B+ circuit.
DTC B25FB 07
The headlamp control module detects a high voltage condition in the headlamp
leveling control module
- right B+ circuit.
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 Testing
1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the
appropriate E13
Headlamp Assembly. It may take up to 2 min for all vehicle systems to power
down.
2. Test for less than 10 Ω between the ground circuit terminal 2 and ground.
- Ignition OFF.
- 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. Ignition ON.
4. Verify a test lamp illuminates between the B+ circuit terminal 6 and ground.
- If the test lamp does not illuminate
- Ignition OFF, disconnect the X5 harness connector at the X50A Fuse Block
- Underhood.
- Test for infinite resistance between the B+ circuit terminal 6 and
ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- Go to next step: If infinite resistance
- 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. Replace the E13 Headlamp Assembly.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- Headlamp Replacement
- Engine Wiring Harness Fuse Block Bracket Replacement
- Control Module References for Headlamp Control Module replacement,
programming, and
setup
READ NEXT:
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.
Diag
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.
Diag
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.
Diag
SEE MORE:
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 Descriptor
DT
System Overview
The engine cooling fan system consists of 2 electric cooling fans and 3 fan
relays. The cooling fan relays
are arranged in a series/parallel (S/P) configuration. This allows the engine
control module (ECM) to
operate both fans together at low or high speeds using 2 fan control circ