I've heard the horror stories about premature DEF heater failure issues. Knowing that GM has extended the warranty on the DEF heater for ten years, didn't really bring me that much comfort. At least mine failed under warranty. After six years and 27k miles my 2015 Chevy DEF heater took a dump. Had GM not extended the warranty it would have cost me 1k at least. Am surprised GM's engineers cannot fix this issue.