B2645

DTC B2645

DTC DESCRIPTOR

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

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

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 1.75 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a low reference ground and a 5-volt reference signal to the ambient light sensor. The BCM monitors the daytime running lamps (DRL) ambient light sensor signal circuit to determine if outside lighting conditions are correct for either DRL or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In high outside light 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

DTC B2645 02
This DTC will set when the BCM detects a short to ground in the DRL ambient light sensor signal circuit.

DTC B2645 05
This DTC will set when the BCM detects a short to voltage or an open in the DRL ambient light sensor signal circuit.

ACTION TAKEN WHEN THE DTC SETS
When DTC B2645 02 or B2645 05 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, install a scan tool and display the Ambient Light Sensor parameter in the BCM data list. The scan tool should display between 1-5 volts.
- If the scan tool parameter is less than 1 volt, repair the DRL ambient light sensor signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ambient light sensor.
- If the scan tool parameter is greater than 5 volts, repair the DRL ambient light sensor signal circuit for a short to voltage.
3. If all circuits test normal, replace the BCM.

REPAIR INSTRUCTIONS

IMPORTANT: Always 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