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 Descriptors

DTC B2580 01 : Headlamp High Beam Control Circuit Short to Voltage
DTC B2580 06 : Headlamp High Beam Control Circuit Open or Short to Ground

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Flash to Pass Switch Signal | 1 | 1 | 1 | --
Headlamp Dimmer Switch High Beam Signal | 1 | 1 | 1 | --
Headlamp Switch Headlamps On Signal | 1 | 1 | 1 | --
Headlamp Switch Headlamps Off Signal | 1 | 1 | 1 | --
Headlamp High Beam Relay Control | B2580 06 | B2580 06 | B2580 01 | --
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 | -- | --
Turn Signal/Multifunction Switch Ground | -- | 1 | -- | --
1. Headlamps Malfunction

### Circuit/System Description

With the headlamp switch in the HEAD position, the headlamp switch headlamp ON signal circuit is grounded through the turn signal/multifunction switch at G300. In response to this input, the body control module (BCM) provides ground to either the headlamp low beam relay control circuit or the headlamp high beam relay control circuit. The position of the headlamp dimmer switch determines which relay coil has ground. The BCM supplies ground to the relay coil circuits, if the headlamps are necessary. The underhood fuse block supplies battery positive voltage to both relay switch circuits. When the low beam relay coil is energized, current flows through the LT LOW beam and the RT LOW beam fuses to the low beam headlamps. When the headlamp high beam relay coil is energized, current flows through the LT HI beam and the RT HI beam fuses to the high beam headlamps. Ground for the left headlamp assembly is provided at G101. Ground for the right headlamp assembly is provided at G102.

### Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

#### B2580 01

This DTC will set when the BCM detects a short to voltage in the headlamp high beam relay control circuit.

#### B2580 06

This DTC will set when the BCM detects a short to ground or an open/high resistance in the headlamp high beam relay control circuit.

### Actions Taken When the DTC Sets

#### B2580 01

When this DTC is present, the high beam headlamps will not operate.

#### B2580 06

When this DTC is present, the high beam headlamps will remain ON.

### 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 high beam relay.
2. Connect a test lamp between the B+ circuit terminal 85 and the relay control circuit terminal 86.
3. Command the High Beam Headlamps 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 high beam relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

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