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 Low Voltage

DTC B2645 07
- Ambient Light Sensor Circuit High Voltage

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 1.4-4.5 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 or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the daytime running lights ON. During low light conditions the BCM will command the low beam headlamps ON.

Conditions for Running the DTC

Ignition ON

Conditions for Setting the DTC

B2645 03

The BCM detects a voltage below threshold on the signal circuit.

B2645 07

The BCM detects a voltage above threshold on the signal circuit.

Action Taken When the DTC Sets

The condition for setting the DTC is not longer present.

Conditions for Clearing the DTC

The condition for setting the DTC is not longer present.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights 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 (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)

Circuit/System Verification

Ignition ON, observe the scan tool Ambient Light Sensor parameter. The reading should be between 1.4-4.5 V and change with ambient light changes.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor.
2. Disconnect the negative terminal of the C1 Battery.
3. Test for less than 5 ohm between the ground circuit harness connector terminal 5 and ground.

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

4. Reconnect the negative terminal to the C1 Battery.
5. Ignition ON, test for 4.8-5.2 V between the signal circuit harness connector terminal 1 and ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.

6. If all circuits test normal, test or replace the B10B Ambient Light/Sunload Sensor.

Component Testing

Static Test
1. Ignition ON, observe the scan tool Ambient Light Sensor parameter. The reading should be between 1.4-4.5 V and change with ambient light changes.
2. Test the B10B Ambient Light/Sunload Sensor by varying the ambient light while monitoring the sensors voltage output.
3. Verify that the voltage output is within the range of the specification.

• If not within the specified range, replace the B10B Ambient Light/Sunload Sensor.

Repair Instructions

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

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