B2580

DTC B2580

Diagnostic Instructions

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

DTC Descriptor
DTC B2580 00
- Headlamp High Beam Control Circuit

Diagnostic Fault Information





Circuit/System Description

The HDM and high beam relay receive battery voltage directly from the battery. The BCM supplies a 100% duty cycle PWM ground signal to the HDM for automatic low beam headlamp control and normal low beam headlamp operation. The BCM also supplies ground to the high beam relay coil for high beam headlamp operation. When the driver places the headlamp switch in the HEADLAMP position and the dimmer switch is in the low beam position, the HDM switches to full output sending current flow through the left and right low beam headlamp fuses to both low beam headlamps. The dimmer switch sends a ground signal to the BCM in the high beam position and a momentary ground signal in the flash-to-Pass (FTP) position from G102 to deactivate the low beam headlamps and activate the high beam headlamps. With the headlamps in the low beam position, the high beams may be momentarily turned on or flashed by activating the FTP portion of the switch.

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

* When the BCM receives a high beam headlamp request the high beam headlamp relay control circuit is shorted to voltage.
* When the BCM is not receiving a high beam headlamp request the high beam headlamp relay control circuit is open or shorted to ground.

Action Taken When the DTC Sets

The high beam headlamps are inoperative or always on.

Conditions for Clearing the DTC

* This DTC will clear on current status after the condition for setting the fault is corrected.
* A history DTC will clear after 100 consecutive ignition cycles without a fault present.

Reference Information
Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Schematics)
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)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the HI HEADLAMP relay.
2. Verify a test lamp does not illuminate between the control circuit terminal 87 and B+.

• If the test lamp illuminates, test the control circuit for a short to voltage.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

• If the test lamp does not illuminate,test the B+ circuit for a short to ground or an open/high resistance.

4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Connect a test lamp between the relay control circuit terminal 86 and B+.
6. Operate the high beam headlamps ON and OFF. 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.

7. If all circuits test normal, replace the HI HEADLAMP relay.

Repair Instructions

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

Control Module References (Programming and Relearning) for BCM replacement, programming, and setup