To the top of the document
Orlando
   
GMDE Start Page Load static TOC Load dynamic TOC Help?

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 Signals Correlation Malfunction

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Headlamp Switch Park Lamp Signal

2

B257A 00

2

--

Headlamp Switch On Signal

B257A 00

1

1

--

Headlamp Switch Headlamps Off Signal

B257A 00

1

1

-

Headlamp Switch Ground

--

1

--

--

1. Headlight Auto Function Only

2. Headlight Auto Function Disabled

Circuit/System Description

When the headlamp switch is placed in the dipped beam or park position, the body control module (BCM) will receive a ground signal through the headlamp switch headlamps signal circuit and the park lamp switch signal circuit.

Conditions for Running the DTC

The ignition is in the ON, ACCESSORY or RUN position.

Conditions for Setting the DTC

The BCM receives an unexpected signal along either the headlamp switch OFF circuit or the headlamp 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

Exterior Lamps Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

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, observe the scan tool Headlamps On Switch, Park Lamps Switch and Automatic Headlamps Disable Switch parameters while selecting the headlamp control switch between the Off, park lamps and headlamps settings. Each parameter should be Inactive and change to Active as each setting is selected.

Circuit/System Testing

  1. Ignition OFF, disconnect the S30 Headlamp Switch.
  2. Test for less than 5 Ω between the ground circuit terminal 6 and ground.
  3. If greater than the specified value, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Park Lamps Switch parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
  6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the ground circuit terminal 6. Verify the scan tool Park Lamps Switch parameter is Active.
  7. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  8. Verify the scan tool Headlamps On Switch parameter is Inactive.
  9. If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
  10. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the ground circuit terminal 6. Verify the scan tool Headlamps On Switch parameter is Active.
  11. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  12. Verify the scan tool Automatic Headlamps Disable Switch parameter is Inactive.
  13. If not the specified value, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
  14. Install a 3 A fused jumper wirebetween the signal circuit terminal 5 and the ground circuit terminal 6. Verify the scan tool Automatic Headlamps Disable Switch parameter is Active.
  15. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
  16. If all circuits test normal, replace the S30 Headlamp Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Headlamp Switch Replacement
    • Control Module References for BCM replacement, setup and programming
   


© Copyright Chevrolet. All rights reserved