2010 Cadillac CTS Sedan AWD V6-3.6L Page 200

2010 Cadillac CTS Sedan AWD V6-3.6L Page 200

Instructions) provides an overview of the diagnostic category.

DTC Descriptor

DTC B257A 00

- Headlamp Switch Input Signals Mismatch

Diagnostic Fault Information

Circuit/System Description

When the turn signal/multifunction 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 turn signal/multifunction switch headlamps ON signal circuit and the park lamp switch signal

circuit are both open and have no ground signal. When the turn signal/multifunction 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.

Actions Taken When the DTC Sets

* When DTC B257A 00 is present on the headlamp switch headlamps OFF signal circuit, the low beam headlamps are always ON in the

AUTO position. The headlamp switch operates in all positions other than AUTO. The AUTO headlamp defeat is inoperative.

* When DTC B257A 00 is present on the headlamp switch headlamps ON signal circuit, the low beam headlamps are always ON. The BCM

disregards all headlamp switch inputs.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.

* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

* Headlights/Daytime Running Lights (DRL) Schematics (See: Diagrams/Electrical Diagrams/Lighting and Horns/System

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

* Exterior Lights Schematics (See: Diagrams/Electrical Diagrams/Lighting and Horns/System Diagram/Exterior Lights Schematics)

Connector End View Reference

Component Connector End Views (See: Diagrams/Connector Views)

Description and Operation

Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems Description