B2645

DTC B2645

DTC DESCRIPTOR

DTC B2645 03: Ambient Light Sensor Circuit Below Threshold

DTC B2645 07: Ambient Light Sensor Circuit Above Threshold




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 depending on outside lighting conditions. The body control module (BCM) provides a 10-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 low in the ambient light sensor signal circuit.

B2645 07: The DTC will set when the BCM detects voltage is above 10 volts in the ambient light sensor signal circuit

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. Turn the ignition OFF.
2. Disconnect the ambient light sensor.
3. Turn the ignition ON.
4. Install a scan tool and display the Ambient Light Sensor parameter in the BCM data list.
- If the scan tool parameter is less than 7 volts, locate and repair an open, high resistance, or short to ground in the ambient light sensor signal circuit, or replace the ambient light sensor.
- If the scan tool parameter is greater than 10.5 volts, locate and repair a short to voltage in the ambient light sensor signal circuit.
5. If circuits test OK, replace the BCM.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Ambient Light Sensor Replacement
- Control Module References for BCM replacement, setup, and programming