Two problems related to diesel engine have been reported for the 2005 GMC Sierra. The most recently reported issues are listed below.
Overheating of 2005 GMC duramax diesel engine while pulling small 5th wheel in mountains of colorado. This caused me to have to slow down to the point where I was a hazard to myself and others on the highways because of my vehicle causing a traffic obstruction.
Engine overheat, requiring pulling off to shoulder, no a/c for occupants of vehicle including two small children.