B2645

DTC B2645

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 B2645
- Ambient Light Sensor Circuit

Circuit/System Description

The body control module (BCM) monitors the daytime running lamps (DRL) ambient light sensor signal circuit in order to determine if the DRL or the headlamps should be turned ON in the automatic lamp control (ALC) mode. When the BCM senses the ambient light sensor voltage is between 1-4.9 volts, either the DRL or the headlamps will be commanded ON.

Conditions for Running the DTC

The system voltage must be between 9-16 volts.

Conditions for Setting the DTC

When the DRL ambient light sensor signal voltage is less than 1 volt or more than 4.9 volts.

Action Taken When the DTC Sets

The headlamps will remain ON in any ambient light state during ALC mode.

Conditions for Clearing the DTC

* This DTC will clear on current status after the condition for setting the fault is corrected.
* A history DTC will clear after 100 consecutive ignition cycles without a fault present.

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 ambient light sensor.
2. Ignition ON, verify the scan tool ambient light sensor parameter is 5 volts.

• If not the specified value, test the DRL ambient light sensor signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.

3. Test the ambient light sensor ground circuit terminal B for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ambient light sensor.

Repair Instructions

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

Control Module References (Programming and Relearning)