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 Descriptors

DTC B2645 03
- Ambient Light Sensor Circuit Below Threshold

DTC B2645 07
- Ambient Light Sensor Circuit Above Threshold

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 depending on outside lighting conditions. The body control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The 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. In low light conditions, when the headlamps switch is in AUTO position, the BCM will command the low beam headlamps ON.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B2645 03

The DTC will set when the BCM detects voltage is below 0.196 volt in the ambient light sensor signal circuit.

B2645 07

The DTC will set when the BCM detects voltage is above 4.9 volts in the ambient light sensor signal circuit or if the ambient light sensor ground circuit is open.

Action Taken When the DTC Sets

When DTC B2645 03 or B2645 07 is present, the ALC will default to ON.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* You issue a scan tool CLEAR DTCs command.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Circuit/System Testing

1. Ignition OFF, disconnect the ambient light sensor.
2. Ignition ON, monitor the Ambient Light Sensor parameter in the BCM data list with a scan tool.

• If the scan tool parameter is less than 0.2 volt, test for a short to ground in the ambient light sensor signal circuit. If a short to ground is not found, replace the BCM.
• If the scan tool parameter is greater than 4.9 volts, test for an open or short to voltage in the ambient light sensor signal circuit or an open in the ambient light sensor ground circuit. If any of those conditions are not found, replace the ambient light sensor.

Repair Instructions

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

* Ambient Light Sensor Replacement
* Control Module References for BCM replacement, setup, and programming Programming and Relearning