Buick Regal: DTC B257C or B257D
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 B257C 00
Left Headlamp Assembly Malfunction
DTC B257D 00
Right Headlamp Assembly Malfunction
Circuit/System Description
The headlamp control module calculates the headlamp angle and sends commands
to the left and right
adaptive forward lighting system headlamp actuators. The headlamp actuators
drive the headlamps to
the position commanded by the headlamp control module. The headlamp control
module monitors the
headlamp actuator motor control circuits for proper circuit continuity and for
shorts to ground or
voltage. If a malfunction is detected, a DTC will be stored in memory and the
driver will be notified
with a "Service AFL Lamp" message displayed over the driver information center
located on the
instrument cluster.
Conditions for Running the DTC
- Battery voltage must be between 9 - 16 V.
- Engine RUNNING.
- Headlamps ON.
Conditions for Setting the DTC
DTC B257C 00
The headlamp control module receives a serial data message from the left
headlamp internal logic
module that an internal headlamp malfunction has occurred.
DTC B257D 00
The headlamp control module receives a serial data message from the right
headlamp internal logic
module that an internal headlamp malfunction has occurred.
Actions Taken When the DTC Sets
- The headlamp control module disables the AFL system.
- The driver information center will display AFL Lamps Need Service.
- On vehicles equipped with both AFL and headlamp leveling, the headlamp
leveling system will
remain active.
Conditions for Clearing the DTC
- The condition responsible for setting the DTC no longer exists.
- A history DTC will clear once 50 consecutive malfunction-free ignition
cycles have occurred.
Diagnostic Aids
DTC B257C and B257D will set when there is an internal malfunction within the
left or right headlamp
assemblies. No parts are serviceable within the headlamp assemblies so complete
headlamp assembly
replacement is necessary.
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 DTC B257C or B257D is not set.
- If DTC B257C or B257D is set
- Program the K26 Headlamp Control Module.
- Verify the DTC does not set.
- If the DTC sets, replace the appropriate E13 Headlamp Assembly.
- Go to next step: If the DTC does not set
- All OK.
- Go to next step: If DTC B257C or B257D is not set
3. All OK
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- Headlamp Replacement
- Control Module References for Headlamp Leveling 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 prior to using this diagnostic
procedure: Diagnostic
System Check - Vehicle
Review the description of Strategy Based Diagnosis: Strategy Based
Diagnosis
An overview of each diagnostic category can be found here: Diagnostic
Proced
NOTE: Examples used in this article are general in nature and do not
necessarily
relate to a specific engine or system. Illustrations and procedures have
been chosen to guide mechanic through engine overhaul process.
Descriptions of processes of cleaning, inspection, assembly and machine
shop prac