For 1990-2009 cars

### 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 B2575 00: Headlamp Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Headlamp Low Beam Relay Control | 2 | 1 | B2575 00 | --
1. Headlamps Inoperative - Low Beams 2. Headlamps Always On - Low Beams

### Circuit/System Description

The low beam headlamps are controlled by the body control module (BCM). The BCM grounds the headlamp low beam relay control circuit in order to energize the HID/LO BEAM relay coil. The HID/LO BEAM relay then sends voltage to the low beam headlamps.

### Conditions for Running the DTCs

• | The headlamps are commanded ON.

• | The headlamp dimmer switch must be in the low beam position.

### Condition for Setting the DTC

The headlamp low beam relay control circuit is shorted to voltage.

### 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

#### 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, command the Low Beam ON with a scan tool. The Low Beam Relay Command parameter should display On and the low beam headlamps should illuminate.

### Circuit/System Testing

1. Ignition OFF, disconnect the HID/LO BEAM relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

3. If all circuits test normal, replace the BCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Control Module References for BCM replacement, setup, and programming