B258A

DTC B258A

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC B258A 01
- Low Beam Control Circuit Short to Battery

Diagnostic Fault Information





Circuit/System Description

The body control module (BCM) switches the headlamp low beams ON as soon it receives a signal from the headlamp switch or ambient light sensor. When this signal is received by the BCM, it applies a voltage through the low beam supply circuits which illuminates the low beams.

Conditions for Running the DTC

The headlamp switch is in the low beam position.

Conditions for Setting the DTC

The BCM detects a short to battery on the low beam control circuit.

Action Taken When the DTC Sets

Headlamp low beam malfunction.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information
Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, command the appropriate Headlamp Low Beam ON and OFF with a scan tool. The appropriate low beam lamp should turn ON and OFF when changing between the commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate E13 headlamp assembly.
2. Ignition OFF, scan tool OFF, exterior lamps OFF, test for less than 5.0 ohm between the ground circuit terminal 1 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 3 and ground.
4. Command the appropriate Headlamp Low Beam ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 BCM.

5. If all circuits test normal, test or replace the E13 headlamp assembly.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Headlamp Replacement (Headlamp Replacement)
* Headlamp Bulb Replacement (TT2) (Headlamp Bulb Replacement (TT2))Headlamp Bulb Replacement (TT4 Low Beam) (Headlamp Bulb Replacement (TT4 Low Beam))Headlamp Bulb Replacement (TT4 High Beam) (Headlamp Bulb Replacement (TT4 High Beam))
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming