2010 Cadillac Truck Escalade RWD V8-6.0L Hybrid Page 633
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 resistor via the DRL resistor control circuit. When the BCM applies ground
to the DRL resistor control circuit, the DRL signal circuits to the right and left headlamp assemblies are pulled low. The DRL signal circuits are
direct inputs to the right and left headlamp control modules. When the DRL signal circuits are provided with ground, the right and left headlamp
control modules respond by turning OFF the low beam headlamps and activating the DRLs. Any function or condition that turns the headlamps ON
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 resistor control circuit.
Action Taken When the DTC Sets
* The Service Headlamp Assembly indicator is commanded ON.
* The BCM will disable the DRL resistor control circuit.
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 (See: Diagrams/Electrical Diagrams/Lighting and Horns/System
Diagram/Headlights/Daytime Running Lights (DRL) Schematics)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (See: Lighting and Horns/Description and Operation/Exterior Lighting Systems Description
and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Circuit
Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic
Procedures/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/General
Electrical Diagnostic Procedures/Circuit Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/General Electrical Diagnostic Procedures/Wiring
Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the DRL resistor.
