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 MismatchDiagnostic 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 | B2057A 00 | B257A 00 | -- |
Headlamp Switch On | 1 | 2 | B2575 00 | -- |
Headlamp Ground | -- | B257A 00 | 2 | -- |
| ||||
Circuit/System Description
When the headlamp switch is in the OFF position, the body control module (BCM) receives a ground signal through the headlamp switch OFF circuit and an open signal on the park lamp ON circuit. When the headlamp switch is in the PARK or HEAD position, the BCM receives an open signal through the headlamp switch OFF circuit and a ground signal through the park lamp ON circuit.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The BCM receives an unexpected signal along either the headlamp switch OFF circuit or the park lamp ON circuit.
Action Taken When the DTC Sets
The BCM disregards the headlamp switch input and defaults to automatic headlamp function.
Conditions for Clearing the DTC
The BCM clears this code from current when the fault is removed from the system.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Ignition ON, headlamp switch to PARK, just the park lamps should illuminate.
Circuit/System Testing
- Headlamp switch to OFF, disconnect the BCM connector C2.
- Ignition to ON, connect a test lamp between the headlamp OFF switch circuit and the positive battery terminal. Verify the test lamp illuminates.
- Headlamp switch to PARK, verify the test lamp is not illuminated.
- Headlamp switch to PARK, connect a test lamp between the park lamp switch ON circuit and the positive battery terminal. Verify the test lamp illuminates.
- Headlamp switch to OFF, verify the test lamp does not illuminate.
- If all circuit/connections test normal, replace the BCM.
| ⇒ | If the test lamp does not illuminate: |
| • | Test for a short to voltage or an open in the headlamp OFF switch circuit. |
| • | Test for an open in the headlamp ground circuit. |
| • | If the circuit/connections test normal replace the headlamp switch. |
| ⇒ | If the test lamp illuminates, test for a short to ground in the headlamp OFF switch circuit. If the circuit/connections test normal, replace the headlamp switch. |
| ⇒ | If the test lamp does not illuminate, test for a short to voltage or an open in the park lamp switch ON circuit. If the circuit/connections test normal, replace the headlamp switch. |
| ⇒ | If the test lamp does illuminate, test for a short to ground in the park lamp switch ON circuit. If the circuit/connections test normal, replace the headlamp switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
