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 Circuit | B2575 00 | B2575 00 | B2575 00 | --
Headlamp Low Beam Relay Battery Supply Voltage Circuit | B2575 00 | B2575 00 | -- | --

### 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 LO BEAM relay coil. The LO BEAM relay then sends voltage to the low beam headlamps.

### Conditions for Running the DTCs

• | The headlamps are commanded ON.

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

### Conditions for Setting the DTC

One or more of the following conditions are present:

• | The headlamp low beam relay control circuit is open, shorted to ground, or shorted to voltage.

• | The headlamp low beam relay battery supply voltage circuit is open or shorted to ground.

### 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.

• | The BCM receives the clear code command from the scan tool.

### Reference Information

#### Schematic Reference

Headlights Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Output Controls

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

Ignition ON, activate the Low Beam output control on the scan tool. The Low Beam Relay Command parameter in the data list should display On and the low beam headlamps should illuminate.

### Circuit/System Testing

1. Ignition OFF, disconnect the underhood fuse block connector C4 and test for a short to voltage, short to ground, an open, or high resistance at the connector terminal K2.
2. Activate the headlamp switch, place the headlamp dimmer switch in the low beam position, and test for a ground signal at the underhood fuse block connector C4 terminal K2.

⇒ | If a ground signal is present, replace the underhood fuse block. If a ground signal is not present, replace the BCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming