2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 672

2010 Cadillac Truck Escalade EXT AWD V8-6.2L Page 672

DTC B2600 (With X88, Z75, and Z88)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System

Check - Vehicle) prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an

overview of the diagnostic approach.

* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure

Instructions) provides an overview of each diagnostic category.

DTC Descriptor

DTC B2600 00

- Daytime Running Lamp Control Circuit

Diagnostic Fault Information

Circuit/System Description

The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between

0.2 and 4.9 V depending on outside lighting conditions. The body control module (BCM) provides a 5 V reference signal to the ambient light

sensor. The body control module (BCM) monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for

either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions,

the BCM will command the DRLs ON by applying ground to the DRL relay via the DRL relay control circuit. When the BCM applies ground to

the DRL relay control circuit, the DRL relay coil energizes causing the relay switch contacts to close. With the DRL relay energized, voltage is

applied through the relay switch contacts, the DRL Resistor, and the DRL fuse to the left and right low beam headlamp fuses illuminating the low

beam headlamps. Any function or condition that turns the headlamps ON will cancel DRL operation. Any function or condition that turns on the

headlamps will cancel DRL operation.

Conditions for Running the DTC

* Battery voltage must be between 9-16 V.

* Headlamp switch in AUTO position.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets