Three problems related to engine exhaust system have been reported for the 2020 GMC Sierra 1500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2020 GMC Sierra 1500 based on all problems reported for the 2020 Sierra 1500.
Tick sound coming from underneath. Also fumes smell. Dealership found it to be the exhaust system. Said the muffler valve is bad. Quoted me $2000 for repair. Never heard of a exhaust system failure in only 5 years. Very unsatisfied with this.
A very strong "ammonia" odor comes into the cabin. This happens when the def fluid is going into the exhaust system for the regen process. The odor makes people inside nauseous and dizzy. Must open widows or stop and get out of the vehicle. Our GMC dealer can find no codes or problems with the exhaust system. We have also noticed that the def fluid has gone down very quickly sometimes during this event. It is random. Some days nothing, other trips 3 and four times that the odor occurs. Looking online- there have been many post about this problem.
Vehicle equipped with l87 6. 2l. At 197 miles engine suddenly ceased operating and would not restart. This occurred while stopped on private road. Vehicle had to be towed to dealership where they found p0300 and diagnosed broken #4 cylinder exhaust valve spring.