B2647

DTC B2647 or B2648

Circuit Description

The body control module (BCM) monitors the ambient light sensor signal circuit in order to determine if the daytime running lights (DRL) or the auto headlights (ALC) should be turned ON in the AUTO mode. When the BCM senses the ambient light sensor signal voltage is between 1.75-4.9 volts, either the DRL will be commanded ON or the ALC will be commanded ON depending upon the amount of light received by the sensor.

DTC Descriptors

This diagnostic procedure supports the following DTC:

* DTC B2647 Ambient Light Sensor Circuit Low
* DTC B2648 Ambient Light Sensor Circuit High

Conditions for Running the DTC

The system voltage must be between 9-16 volts.

Conditions for Setting the DTC

* When the ambient light sensor signal voltage is less than 1.75 volts
* When the ambient light sensor signal voltage is more than 4.9 volts

Action Taken When the DTC Sets

The ALC will remain always ON or always OFF in any ambient light state.

Conditions for Clearing the MIL/DTC

* This DTC will clear immediately after the condition for setting the fault is corrected.
* A history DTC will clear after 100 consecutive ignition cycles without a fault present.
* Use a scan tool in order to clear history and current DTCs.

Test Description

Step 1 - Step 11:

Step 12 - Step 13:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that the value displayed is within the specified range.
3. This step tests for the proper operation of the circuit in the high voltage range.
4. This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.