P21DD diagnostic code

[Car54]

My check engine light came on in my 2016 chev. 2500 hd, so I ran a code check and it is the DEF heater failure. Called nearest dealership (65) miles booked out until May 24th the next closest dealership is around 200 miles. In reviewing other forums people are saying the issue covered under warranty due to this being a problem with many of the LML Duramax engines. People are also saying it will go into limp mode if I continue to drive it. Anyone else have this issue and did you continue to drive it. I would like to get fixed soon just don't want a tow bill trying to drive 200 plus miles to dealership.