Circuit Description
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The auxiliary HVAC control module monitors the air temperature in the lower auxiliary discharge duct via a lower auxiliary air temperature sensor. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low. The auxiliary HVAC control module converts this voltage to a digital signal that can be transmitted over the keyboard display driver (KDD) data bus to the HVAC control module. The HVAC control module contains the logic that monitors the auxiliary air temperature and is responsible for setting the DTC.