B2600

DTC B2600

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 B2600 00
- Daytime Running Lamp Control Circuit

Diagnostic Fault Information





Circuit Description

The ambient light sensor is a light sensitive transistor that varies the voltage signal to the body control module (BCM) based on outside lighting conditions. When the ambient light sensor indicates daytime conditions, the body control module (BCM) grounds the DRL relay control circuit energizing the DRL relay. With the DRL relay energized, the switch contacts close and voltage is applied to the DRL 1 and DRL 2 fuses to the left and right low beam headlamps. Any function or condition that turns on the headlamps will cancel DRL operation.

Conditions for Running the DTCs

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The BCM detect a short to voltage in the DRL relay control circuit.

Action Taken When the DTC Sets

The BCM will deactivate the DRL relay for the remainder of the ignition cycle.

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 (Connector 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 Testing

1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
2. Connect a test lamp between B+ and the control circuit terminal H2.
3. Command the DRL 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 all circuits test normal, replace the underhood fuse block.

Repair Instructions

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

* Accessory Wiring Junction Block Replacement (Accessory Wiring Junction Block Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming