B2575

DTC B2575

Diagnostic Instructions

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

DTC Descriptor

DTC B2575 00
- Headlamp Control Circuit

Diagnostic Fault Information






Circuit/System Description

The low beam headlamps are controlled by two different inputs to the body control module (BCM), the headlamp switch, or when in the Auto mode, the ambient light sensor. When the BCM receives a low beam headlamps ON command, it grounds the headlamp low beam relay control circuit in order to energize the low beam PCB relay. With the relay energized, battery voltage is applied through switch side of the relay, both LO BEAM fuses, and the low beam supply voltage circuits to the low beam headlamps.

Conditions for Running the DTC

* The low beam headlamps are commanded ON.
* The headlamp dimmer switch must be in the low beam position.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

The BCM will deactivate the headlamp low beam PCB relay for the remainder of the ignition cycle.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

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 A5 and B+.
3. Ignition ON, 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, replace the underhood fuse block.

Repair Instructions

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

* Accessory Wiring Junction Block Replacement.