B2580

DTC B2580

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC B2580 00
- Headlamp High Beam Control Circuit




Diagnostic Fault Information






Circuit/System Description

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


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 voltage on the headlamp high beam relay control circuit while trying to apply a ground to energize the relay.


Action Taken When the DTC Sets

The BCM turns off the headlamp high beam relay control for the remainder of the ignition cycle.


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.



Reference Information
Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Connector End View Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning) for Scan Tool Information


Circuit/System Verification

Ignition ON, turn headlamps ON and place the turn signal/multifunction switch in the headlamp high beam position. Observe the scan tool High Beam Relay Command parameter. The reading should display On and the high beam headlamps should illuminate.


Circuit/System Testing

Caution: The high intensity discharge system produces high voltage and current. To reduce the risk of severe shocks and burns:

* Never open the high intensity discharge system ballast or the arc tube assembly starter.
* Never probe between the high intensity discharge system ballast output connector and the arc tube assembly.



1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal 19 and B+.
3. Ignition ON, 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.

• 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.

4. If the circuit tests normal, test or replace the underhood fuse block.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Underhood Electrical Center or Junction Block Replacement (Service and Repair)
* Programming and Relearning (Programming and Relearning) for BCM replacement, setup, and programming