Conditions for Setting the DTC: B3933
WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The HVAC control module detects the evaporator temperature sensor signal circuit is less than -36°C (-38°F) or greater than 215°C (419°F) for more than 15 seconds.