My check engine light came on so I ran code check which showed DEF reluctant heater failure. I got a letter sometime back from GM stating that this issue was now covered under an extended warranty. My problem is my closest dealership 62 miles, told me they are booked until May 24. I saw on other forums that the truck may go into "limp mode" if I drive it? Has anyone dealt with this issue out there, I have other dealerships 250 miles away just don't want to pay a tow bill trying to get there