B2645

DTC B2645

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC B2645 03
- Ambient Light Sensor Circuit Voltage Below Threshold

DTC B2645 07
- Ambient Light Sensor Circuit Voltage 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 between 0.2 and 4.9 V depending on outside lighting conditions. 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 when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the DRLs ON. During low light conditions the BCM will command the DRLs ON. 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.

Conditions for Setting the DTC

B2645 03

The BCM detects a short to ground in the ambient light sensor signal circuit.

B2645 07

The BCM detects a short to voltage or an open/high resistance in the ambient light sensor signal circuit.

Actions Taken When the DTC Sets

* Automatic lamp control is inoperative.
* The BCM defaults to low light status and commands the low beam headlamps ON.

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 Schematics (Headlights Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B10 ambient light sensor.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal 6 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 V.

• If less than the specified range, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the K9 BCM.

4. Install a 3 A fused jumper wire between the signal circuit terminal 5 and the ground circuit terminal 6. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V.

• 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 K9 BCM.

5. If all circuits test normal, replace the B10 ambient light sensor.

Repair Instructions

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

* Headlamp Automatic Control Ambient Light Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming