My heater was blowing out cold. The dealer said it was a programming issue and they had to download a program from GM in order to fix it. Is this possible?

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The heater fan still worked, the electronic temperature panel still worked, but the heat was blowing out cold. The dealer said I needed an update to some program that they would get through the Internet. Is it possible for an Internet program to cause ONLY the heat to blow out cold and be fixed with a download?