I get a "Transponder error" message on the SV display after a few minutes when sitting inside the hangar or otherwise don't have GPS position within a minute or so of powering up. I have the SV-TXPDR-261. Looking at the transponder setup menu, I can see an explanation for why the "error" message came up. As soon as my position source (GPS-2020) provides the transponder a valid position source, the message goes away.