I purchased this Envoy new and it was great until 58,000 we had the first problem. The service engine light would come on intermittently. The dealer keep changing sensors that never solved the problem. The finally told me the crank shaft bearings were bad. They were replaced under warranty. The light continued to come on. They replaced sensor after sensor it would fix it temporarily but never permanent. At 106,000 miles, the light came on and stayed on. I took it back to the dealer they charged me $850 to replace 2 sensors when that didn't work they called me to inform me I need a new engine at the additional cost of $4,500. Yikes! I was totally feed up at this point so I went and got my Envoy paid the $850 and left.

I had a shade-tree mechanic recommended by a friend look at it for me. In about 45 minutes he had pulled the valve cover and told me the timing chain had jumped 2 notches and that's why the service engine light was on. He found the hydraulic tension pulley was stuck and the chain was loose. He replaced it and now I have 168,000 miles with no service lights. I feel ripped of by GMC because they charged me a fortune and never fixed my Envoy. They are total morons! Moral of the story: If your service engine light indicates the cam sensor won't synchronize with the crank shaft sensor, have a rear mechanic check you timing chain before you let the idiots replace sensors that are not bad.