B2575

DTC B2575

Diagnostic Instructions

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



DTC Descriptor
DTC 2575 00
- Headlamp Control Circuit




Diagnostic Fault Information






Circuit/System Description

Two different inputs to the body control module (BCM) can turn ON the low beam headlamps. The headlamp switch and the ambient light sensor.

Automatic Headlamps Operation

When the ambient light sensor detects a low light condition, the BCM then applies a ground to the headlamp low beam relay control circuit. This energizes the LO BEAM PCB relay and applies voltage through the LO BEAM fuses to the headlamp assemblies.

Headlamp Switch Operation

When the headlamp switch is placed in the ON position, ground is applied to the BCM through the headlamp switch headlamps ON signal circuit. The BCM then applies a ground to the headlamp low beam relay control circuit. This energizes the LO BEAM PCB relay and applies voltage through the headlamp LO BEAM fuses to the headlamps assemblies.


Conditions for Running the DTC

The ignition is ON. The headlamps must be commanded ON by the BCM from inputs by either the headlamp switch or the ambient light sensor.


Conditions for Setting the DTC

The BCM detects a short to voltage on the headlamp low beam relay control circuit while trying to energize the relay.


Action Taken When the DTC Sets

The BCM turns off the headlamp low beam relay control for the remainder of the ignition cycle.


Conditions for Clearing the DTC

* The conditions for setting the DTC are no longer present.
* A history DTC clears after 100 malfunction-free ignition cycles.



Reference Information
Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Diagrams)
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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning) for Scan Tool Information


Circuit/System Verification

Ignition ON, turn the headlamps ON. The headlamps should illuminate.


Circuit/System Testing

1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal 10 and B+.
3. Command the Low Beams 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 ground. If the circuit tests normal, replace the BCM.


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

4. If the circuit tests normal, test or replace the underhood fuse block.



Repair Instructions

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

* Underhood Electrical Center or Junction Block Replacement (Service and Repair)
* Programming and Relearning (Programming and Relearning) for BCM replacement, setup, and programming