One problem related to engine overheat has been reported for the 2005 GMC Sierra. The most recently reported issues are listed below.
05 duramax is running very warm and overheating while towing. Four times we have towed and all four times the truck ran warm the last time the heads up display said engine over heating. This truck is rated to tow 16,000 + pounds and I'm towing around 15,500 and it can't do it without overheating the coolant and transmission.