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 base on the signal from the ambient light sensor.

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 volts or greater than 4.75 volts on 3 consecutive tests.

ACTION TAKEN WHEN THE DTC SETS
Twilight status 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

Steps 1- 2:

Steps 3 - 6:

Steps 7 - 12:

The numbers below refer to the step numbers on the diagnostic table.
3. Tests for the proper operation of the circuit in the high voltage range.
4. 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.