Rear differential warning light flickers

OK news and good news.

OK news is they are replacing the sensor. That may well be it, but I’d guess that is only the first thing they do and if that does not work, they will need to go to step two.

The good news is they are going to foot the bill and it is no longer your problem, other than making sure they get the problem fixed. Keep everything done in writing until you are totally sure they have it fixed.