Had a similar error code on our GMR 41. (using a 3210 chartplotter)... After some investigation, I found that while under shore power, I would get the error code. If I waited until under ships power to start the unit, it would work fine. Somewhere I have a voltage problem or perhaps the radar is being too sensitive. Anyway, Garmin is programmed to say "send it in". I am going to wait and see if I can resolved this on my end (electrically) before handing over $500 bucks to Garmin.