Service Information

Captiva

DTC B257A

Diagnostic Instructions

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

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

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

DTC Descriptor

DTC B257A 00: Headlamp Switch Input Signal Mismatch

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Headlamp Switch Off	B257A 00	B257A 00	B257A 00	-
Park Lamp Switch On	B257A 00	B257A 00	B257A 00	-
Headlamp Switch On	B257A 00	B257A 00	B257A 00	-
Headlamp Switch Ground	--	B257A 00	--	--

When the headlamp switch is in the OFF position, the body control module (BCM) receives a ground signal through the headlamp switch headlamps OFF signal circuit and no signal on the headlamp switch headlamp ON signal circuit and headlamp switch park lamps ON signal circuit. When the headlamp switch is in the PARK or HEAD position, the BCM receives no signal through the headlamp switch headlamps OFF signal circuit and a ground signal through the headlamp switch headlamp ON signal circuit and headlamp switch park lamps ON signal circuit.

•	The conditions for setting the DTC are no longer present.

•	A history DTC clears after 100 malfunction-free ignition cycles.

•	The BCM receives the clear code command from the scan tool.

Reference Information

Schematic Reference

Headlamps/Daytime Running Lamps (DRL) Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, headlamp switch to PARK, just the park lamps should illuminate. Headlamp switch to HEAD, the park lamps and headlamps should illuminate.

Circuit/System Testing

The chart below is to be used to determine when and where a ground signal should be present.

Circuit	AUTO	PARK	HEAD
Headlamp Switch Headlamps Off Signal BCM Terminal 17	Ground	Open	Open
Headlamp Switch Park Lamps Signal BCM Terminal 8	Open	Ground	Ground
Headlamp Switch Headlamps On Signal BCM Terminal 12	Open	Open	Ground

Ignition OFF, disconnect the BCM connector C2 and start with the headlamp switch in the AUTO position. Test each connector circuit listed in the chart for the proper signal.
If voltage is present on any circuit, test that circuit for a short to voltage.

⇒	If the circuit/connections test normal, replace the headlamp and panel dimmer switch.

If no ground signals are present, test the headlamp switch ground circuit for an open.

⇒	If the circuit/connections test normal, replace the headlamp and panel dimmer switch.

If all signal functions of the headlamp and panel dimmer switch circuits test normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Headlamp Switch Replacement

•	Control Module References for BCM replacement, setup, and programming