A Loose or worn gas cap may cause Check Engine Light to illuminate.Google+
Car Problem Reports
GMC Acadia Check Engine Light Due to Gas Cap Issue
GMC Acadia Problem
Average Mileage: 74,600 mi (40,000 mi - 100,000 mi)
Visitor, 2007 GMC Acadia, 54,000 mi
so far, the only thing being talked about with the service center is a diagnostic check for $95 to tell me what the issue is. then it will be on to parts and labor. come on GMC, you can do better!
Visitor, 2007 GMC Acadia, 100,000 mi
I think that is what is wrong now.
Visitor, 2008 GMC Acadia, 90,000 mi
Got a new gas cap
Visitor, 2010 GMC Acadia, 40,000 mi
Gas cap had not been properly tightened to "locked" position, unbeknownst to me. My check engine light came on, and my awesome mechanic figured out the gas cap was causing it (without charging me a dime).
Visitor, 2009 GMC Acadia, 89,000 mi
Check engine light comes on. Replaced original gas cap with a locking gas cap, light turns off and stays off. Can't stand the locking gas cap. I removed the gasket on the original gas cap, turned it around and put it back on the cap. Put the original cap back on. Light stayed off for about a week. Then it came back on. Tried the locking cap again, light would not go out. Played around with the gasket on the original cap and got the light to go out again. I am now looking for an OEM cap to replace the original with.