B2600

DTC B2600

Diagnostic Instructions

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

DTC Descriptor

DTC B2600 00
- Daytime Running Lamp Control Circuit

Diagnostic Fault Information






Circuit Description

Battery positive voltage is applied at all times to both the coil and switched sides of the DRL PCB Relay. The daytime running lamps (DRL) are controlled by the body control module (BCM). The BCM grounds the DRL relay control circuit in order to energize the DRL PCB relay coil. With the relay energized, voltage is applied through the switch side of the relay, both LOW BEAM Fuses, and the headlamp low beam supply voltage circuits to the low beam headlamps.

Conditions for Running the DTCs

* The headlamp switch is in the AUTO position.
* The park brake is unapplied.
* The engine is running.

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.

Circuit/System Verification

Carefully supply sufficient light to simulate daylight conditions to the ambient light sensor. With the engine running, headlamp switch in AUTO position, and the park brake released, the day time running lamps should illuminate.

Circuit/System Testing

1. Ignition OFF, disconnect X3 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal 40 and B+.
3. Ignition ON and headlamps OFF, command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF between 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 underhood fuse block.

Repair Instructions

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

* Underhood Electrical Center or Junction Block Replacement