2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 288

2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 288

Actuator 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.