I had to have my DEF sensor replaced at 54K miles which means the DEF tank gets replaced, the sensor is built into the tank (great design GM , JK). Then 36 hours later that sensor took a crap and had to go back, again. That repair was just short of $800 and at 54,000 miles out of warranty, nice. That part came with a 12K mile or 12 month warranty which would mean that in about 5 months I might be buying another one?? No, that CTD is no longer my problem, its gone after 59,000 and 15 months. Why you may wonder, 3 NOX sensors, 1 particulate matter sensor, 2 DEF sensors, a My stink infotainment center, and a hands free phone system that can't understand a call command. BTW don't think your CTD is worth any more than any other GM product, trade in was less than 50% of new cost, typical GM values.