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 02
- Ambient Light Sensor Circuit Short to Ground
DTC B2645 05
- Ambient Light Sensor Circuit Short to Battery or Open
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 volts depending on outside lighting conditions. The body control module (BCM) provides a low reference ground and 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. During low light conditions the BCM will command the low beam headlamps 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 volts.
Conditions for Setting the DTC
B2645 02
The DTC will set when the BCM detects a short to ground in the ambient light sensor signal circuit.
B2645 05
The DTC will set when the BCM detects a short to voltage or an open in the ambient light sensor signal circuit.
Actions Taken When the DTC Sets
* Automatic lamp control (ALC) 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/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) 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 ambient light sensor.
2. Ignition OFF, exterior lamps OFF, key removed, wait 30 seconds, test for less than 10 ohms between the appropriate low reference circuit terminal listed below and ground.
* Ambient light sensor low reference circuit terminal B - with C60
* Ambient light sensor low reference circuit terminal C - with C68
• If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 volts.
• If less than the specified range, test the appropriate signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the BCM.
* Ambient light sensor signal circuit terminal A - with C60
* Ambient light sensor signal circuit terminal D - with C68
4. Install a 3 A fused jumper wire between the appropriate signal and low reference circuit terminals listed below. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 volts.
* Ambient light sensor signal circuit terminal A and low reference circuit terminal B - with C60
* Ambient light sensor signal circuit terminal D and low reference circuit terminal C - with C68
• 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.
5. If all circuits test normal, replace the ambient light sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Ambient Light Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming