B2646

DTC B2646

Circuit Description

The HVAC control module determines the ambient light conditions either DAYTIME or NIGHT based on the voltage from the ambient light sensor. The HVAC control module provides the ambient light sensor with a 5-volt reference voltage and a signal return circuit. The ambient light sensor signal circuit is a direct input to the HVAC control module. The HVAC control module sends out a class 2 message to the dash integration module (DIM) indicating the outside light condition based on the signal from the ambient light sensor.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2646 Ambient Light Sensor Circuit Range/Performance

Conditions for Running the DTC

The HVAC control module is powered.

Conditions for Setting the DTC

The twilight sensor voltage is less than 0.09 volt or greater than 4.75 volts on 3 consecutive tests.

Action Taken When the DTC Sets

The twilight status is set to NIGHT.

Conditions for Clearing the DTC

The HVAC control module does not detect a voltage that is less than or greater than the predetermined value during the diagnostic self test.

Test Description

Step 1 - Step 10:

Step 11 - Step 12:

The numbers below refer to the step numbers on the diagnostic table.
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.