The DEF fill port is not vented and provides a tight fit with the DEF dispensing hose and nozzle at a truck filling station. The DEF dispensing nozzle cannot be placed entirely in the port since it pressurizes the DEF tank and causes block back spray on the operator. Filling the DEF tank at a truck filling station always results in DEF spillage regardless of the filling technique employed.

- Peoria, AZ, USA

The DEF system does not provide a level indication. Whenever the DEF is filled it always results in a DEF spill to the environment since the operator does not know whether to add 5 gallons or one gallon.

- Peoria, AZ, USA

The DEF fill tube is under the hood on the opposite side of the fuel filling tube. To fill the DEF at a truck stop, one has to park really close to the pumps and stretch the hose across a hot engine. One has to be careful that hot engine does not burn a hole in the DEF hose and cause a spill.

- Peoria, AZ, USA

Lack of proper venting of the DEF holding tank causes tank to buckle and expand resulting in very loud metal banging sounds as vehicle travels between high and low elevations. For example driving from Flagstaff AZ (el. 7000) to Phoenix AZ (el 1600) results in loud metal noises from the tank as it partially implodes due to change in pressure. Should the DEF tank develop cracks the result is a leak in DEF to the environment.

- Peoria, AZ, USA

Severe shake when braking at high speeds, fuel tank failed (vehicle was spewing diesel) - it took 3 months to get a new tank, transfer case has failed multiple times. We have been having these problems since the day we picked up the truck.I have service records showing all the repairs. GM is aware of the problems but claim 'there is nothing they can do but wait for a fix'.

- Milton, NY, USA

When vehicle is accelerating anywhere from 30-50 mph, the truck loses power for several seconds, and starts sputtering or chugging. The RPM on the dash starts bouncing up and down. This goes on for several seconds and truck slows down. It then goes away and can continue driving. However, when towing trailers, the effect is only increased and the truck slows down even more.

- Bozeman, MT, USA