Replacement (Delphi))
* Control Module References (See: Testing and Inspection/Programming and Relearning)for HVAC control module replacement, setup, and
programming
B257A
DTC B257A
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC B257A 00
- Headlamp Switch Input Signals Mismatch
Diagnostic Fault Information
Circuit/System Description
When the headlamp and panel dimmer switch is placed in the AUTO position, the body control module (BCM) receives a ground signal through the
headlamp switch headlamps OFF signal circuit. The headlamp and panel dimmer switch headlamps ON signal circuit and the park lamp switch
signal circuit are both open and have no ground signal. When the headlamp and panel dimmer switch is placed in the PARK or HEAD position, the
BCM will receive a ground signal through the headlamp switch headlamps ON signal circuit and the park lamp switch signal circuit. The headlamp
switch headlamps OFF signal circuit will be open and have no ground signal.
Conditions for Running the DTC
Battery voltage must be between 9-16 V
Conditions for Setting the DTC
The BCM detects a short to ground on the headlamp switch headlamps OFF signal circuit or the headlamp switch headlamps ON signal circuit.
