B257C

DTC B257C

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B257C 00

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Left Headlamp Assembly

Circuit/System Description

On vehicles equipped with adaptive forward lighting, the headlamps can turn left and right to improve visibility during turns.

Conditions for Running the DTCs

* Ignition ON.

* Gear selector in DRIVE.

* Headlamp switch in AUTO position.

* The ambient light sensor indicating Night.

* Vehicle speed greater than 2 km/h (1.3 mph).

* The steering wheel is turned greater than 10 degrees to the right or left.

Condition for Setting the DTC

A malfunction internal to the left headlamp assembly.

Action Taken When the DTC Sets

The adaptive forward lighting system is inoperative for the remainder of the ignition cycle.

Conditions for Clearing the DTC

The conditions for setting the DTC are no longer present.

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views A/C Compressor Clutch

Description and Operation

Exterior Lighting Systems Description and Operation Exterior Lighting Systems

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Programming and Relearning for scan tool information

Circuit/System Verification

Verify that DTC B257C is not set.

If the DTC is set, replace the left headlamp assembly.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

Headlamp Replacement (Acadia) Headlamp Replacement (Traverse with TVP) Headlamp Replacement (Traverse with TVP)Headlamp Replacement (Enclave)