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 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 High Beam Relay Control

B2580 06

B2580 06

B2580 01

--

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

--

LF High Beam Headlamp Voltage Supply

1

1

1

--

LF Low Beam Headlamp Voltage Supply

1

1

1

--

RF High Beam Headlamp Voltage Supply

1

1

1

--

RF Low Beam Headlamp Voltage Supply

1

1

1

--

LF Headlamp Ground

--

1

1

--

RF Headlamp Ground

--

1

1

--

Turn Signal/Multifunction Switch Ground

--

1

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. For more detailed information concerning headlamp operation refer to Exterior Lighting Systems Description and Operation .

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 an open or short to ground 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.
    • You issue a scan tool CLEAR DTCs command.
    • 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

Lighting Systems 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 Testing

  1. Ignition OFF, disconnect the high beam relay.
  2. Connect a test lamp between the high beam relay control circuit and the voltage supply circuit at the high beam relay terminals.
  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.
  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 open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the high 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