GM Service Manual Online
For 1990-2009 cars only

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 Battery

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

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Headlamp High Beam Relay B+

1

1

--

--

Headlamp Low Beam Relay B+

1

1

--

--

Ambient Light Senor Signal

B2645 02

B2645 05

B2645 05

--

Flash to Pass Switch Signal

1

1

1

--

DRL Relay Control

2

2

2

--

Headlamp High Beam Relay Control

B2580 06

B2580 06

B2580 01

--

Headlamp Low Beam Relay Control

1

1

1

--

LF Low Beam Headlamp Control

1

1

1

--

RF Low Beam Headlamp Control

1

1

1

--

Ambient Light Senor Low Reference

--

2

2

--

LF Headlamp Ground

--

1

--

--

RF Headlamp Ground

--

1

--

--

Turn Signal/Multifunction Switch Ground

--

1

--

--

1. Headlamps Malfunction

2. Daytime Running Lamps Malfunction

Circuit/System Description

When the turn signal/multifunction switch is placed in the headlamps high or flash to pass (FTP) position, ground is applied to the body control module (BCM) through the headlamp high beam signal circuit or the flash to pass switch signal circuit. The BCM applies ground to the headlamp high beam relay control circuit which energizes the high beam relay. With the high beam relay energized, the switch contacts close allowing battery voltage to flow through the HI BEAM fuses to the high beam headlamps. Ground for the left headlamp is supplied at G101 and the right headlamp receives ground at G102.

Conditions for Running the DTC

    • Battery voltage must be between 9-16 volts.
    • Headlamps ON.

Conditions for Setting the DTC

B2580 01

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

B2580 06

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

Action Taken When the DTC Sets

    • When DTC B2580 01 is present, the high beam headlamps and flash to pass (FTP) will not operate.
    • When DTC B2580 06 is present, the high beam headlamps will be ON at all times or 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 X2 harness connector at the underhood fuse block.
  2. Connect a test lamp between B+ and the control circuit terminal A2.
  3. Command the High Beams ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  4. 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 an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, replace the underhood fuse block.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Underhood Electrical Center or Junction Block Bracket Replacement
    •  Control Module References for BCM replacement, setup, and programming