Friday, August 9, 2019

2019 Cadillac Truck Escalade AWD V8-6.2L Diagnostic Instructions Page 206


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.

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