B2575

DTC B2575

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 B2575
- Headlamp Low Beam Control Circuit




Diagnostic Fault Information






Circuit/System Description

When the Headlamp switch is placed in the headlamp ON position, ground is applied to the body control module (BCM) through the headlamp signal circuit. The BCM then applies ground to the HDLP relay control circuit closing the relay contacts, allowing voltage to be applied to the RH HDLP and LH HDLP voltage supply circuits. Ground is applied at the HI/LO BEAM relay at all times with the headlamp dimmer switch in the LO BEAM position completing the circuit to the headlamps. Ground for the left headlamp and right headlamp is supplied at G102.


Conditions for Running the DTC

The battery voltage must be between 9-16 volts.


Conditions for Setting the DTC

The headlamp relay control circuit is shorted to voltage.


Action Taken When the DTC Sets

Both headlamps will be on at all times.


Conditions for Clearing the DTC

* This DTC will clear on current status after the condition for setting the fault is corrected and the ignition is cycled.
* 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 (Component Connector End Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information 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

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


Circuit/System Verification

Ignition ON, command the headlamps on and off with a scan tool and verify that the headlamps turn on and off.

If the headlamps do not turn on or remain always on perform the Headlamp CIrcuit/System Test..



Circuit/System Testing

1. Ignition OFF, disconnect the HDLP relay.
2. Connect a test lamp between the control circuit terminal 86 and the B+ circuit terminal 85.
3. Command the low 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 HDLP relay.



Repair Instructions

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

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for BCM replacement, programming, and setup.