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 Low Beam Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Flash to Pass Switch Signal | 1 | 1 | 1 | --
Headlamp Switch High Beam Signal | 1 | 1 | 1 | --
Headlamp Switch Headlamps ON Signal | B257A 00 | 1 | 1 | --
Headlamp Switch Headlamps OFF Signal | B257A 00 | 1 | 1 | --
Park Lamp Switch ON Signal | 2 | B257A 00 | 2 | --
Headlamp High Beam Relay Control | 1 | 1 | B2580 00 | --
Headlamp Low Beam Relay Control | 1 | 1 | B2575 00 | --
LF High Beam Headlamp Control | 1 | 1 | 1 | --
LF Low Beam Headlamp Control | 1 | 1 | 1 | --
RF High Beam Headlamp Control | 1 | 1 | 1 | --
RF Low Beam Headlamp Control | 1 | 1 | 1 | --
LF Headlamp Ground | -- | 1 | -- | --
RF Headlamp Ground | -- | 1 | -- | --
Headlamp and Panel Dimmer Switch Ground | -- | 1 | -- | --
Turn Signal/Multifunction Switch Ground | -- | 1 | -- | --
1. Headlamps Malfunction 2. Park, License, and/or Tail Lamps Malfunction

### Circuit/System Description

When the headlamp and panel dimmer switch is placed in the headlamp position, ground is applied to the body control module (BCM) through the headlamp low beam signal circuit. The BCM then applies ground to the headlamp low beam relay control circuit which energizes the low beam relay. With the low beam relay energized, the switch contacts close allowing battery voltage to flow through the LO BEAM fuses to the low beam headlamps. Ground for the low beam headlamps is supplied at ground G102.

### Conditions for Running the DTC

• | Battery voltage must be between 9-16 volts.

• | Headlamps ON.

### Conditions for Setting the DTC

DTC B2575 00 will set when the BCM detects a short to voltage in the headlamp low beam relay control circuit.

### Actions Taken When the DTC Sets

When DTC B2575 00 is present, the low beam headlamps will not operate.

### 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.

### 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 Testing

1. Ignition OFF, disconnect the low beam relay.
2. Connect a test lamp between the control circuit terminal 85 and the B+ circuit terminal 86.
3. Command the Front Low Beam Test 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 open/high resistance. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the low beam relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Underhood Electrical Center or Junction Block Replacement

• | Relay Replacement

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