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 2575 00
- 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 low beam signal circuit. The BCM then applies ground to the headlamp low beam relay control circuit which energizes the low beam relay. With the low beam relay energized, the switch contacts close allowing battery voltage to flow through the LO HDLP fuses to the low beam headlamps.

Conditions for Running the DTC

* Battery voltage must be between 9-16 V.
* Headlamps ON.

Conditions for Setting the DTC

The BCM detects a short to voltage in the headlamp low beam relay control circuit.

Actions Taken When the DTC Sets

The low beam headlamps 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 Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation

Exterior Lighting Systems Description and Operation Exterior Lighting Systems
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 Control Module References for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the low beam relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

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

3. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

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

4. 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 an open/high resistance.

5. Disconnect the harness connector at the appropriate headlamp - front.
6. Test for less than 5 ohm between the headlamp - front ground circuit terminal B and ground

• If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the headlamp - front.
8. Connect a 20 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the headlamp - front is activated.

• If the headlamp - front does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the headlamp - front.
• If the headlamp - front does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the headlamp - front.

9. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
10. Command the Low 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.

11. If all circuits test normal, test or replace the low beam 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)
* Headlamp Replacement (Chevrolet) Removal and ReplacementHeadlamp Replacement (GMC ) Removal and ReplacementHeadlamp Replacement (HD Chevrolet Diesel) Removal and Replacement
* Control Module References Control Module References for BCM replacement, setup, and programming