A Goodman D2 error fault or code is likely related to a system mismatch. The GTST wall control will still communicate with the equipment, but it will not allow it to run properly as it knows that is not a correct match up. Using Goodman's System Configurator as shown below, will help you determine what components are compatible. The DTA119 Equipment interface, will work in most, if not all applications where the air-handler or furnace is Non-Communicating.