B2645

DTC B2645

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 B2645 02
- Ambient Light Sensor Circuit Short to Ground

DTC B2645 05
- Ambient Light Sensor Circuit Short to Battery or Open

Circuit/System Description

The body control module (BCM) monitors the ambient light sensor signal circuit in order to determine if the daytime running lights (DRL) or the automatic lamp control (ALC) should be turned ON in the AUTO mode. When the BCM senses the ambient light sensor voltage is between 1.75-4.9 volts, either the DRL will be commanded ON or the ALC will be commanded ON.

Conditions for Running the DTC

The system voltage must be between 9-16 volts.

Conditions for Setting the DTC

B2645 02

Will set if there is an open or short to ground in the ambient light sensor signal circuit.

B2645 05

Will set if there is an open or short to voltage or an open in the ambient light sensor signal circuit.

Action Taken When the DTC Sets

The ALC will remain ON in any ambient light state.

Conditions for Clearing the DTC

* The conditions for setting the DTC are no longer present.
* A history DTC clears after 100 malfunction-free ignition cycles.

Circuit/System Testing

1. Ignition OFF, disconnect the ambient light sensor.
2. Ignition ON, verify the scan tool ambient light sensor parameter is 0.02 volts.

^ If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ambient light sensor.
^ If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

3. If all circuits test normal, replace the BCM.

Repair Instructions

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

* Ambient Light Sensor Replacement