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 B2580 00: Headlamp High Beam Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Headlamp High Beam Relay Control | B2580 00 | B2580 00 | B2580 00 | --

### Circuit/System Description

Voltage is applied at all times to the high beam headlamp relay from battery voltage. When the multifunction switch is placed in either the FTP or HIGH position, ground is applied to the body control module (BCM). The BCM then applies a ground to the headlamp high beam relay control circuit. This engages the relay and applies voltage through the HI HEADLAMP fuses to both left and right high beam headlamps.

### Conditions for Running the DTC

The ignition is ON. The high beam headlamps must be commanded ON by the multifunction switch.

### Conditions for Setting the DTC

The BCM detects a short to ground, open, high resistance, or short to voltage on the headlamp high beam relay control circuit.

### Action Taken When the DTC Sets

The high beam headlamps are inoperative.

### 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 High Beam output control on the scan tool. The High Beam Relay Command parameter in the data list should display On and the high 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 H4.
2. With a scan tool, activate the High Beams output control on the scan tool and test for ground at the underhood fuse block connector C4 terminal H4.

⇒ | 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