Computer problem
2008 GMC Yukon V8 Two Wheel Drive Automatic 8900 miles
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I filled my truck up with gas yesterday and I think I put the gas cap on wrong, After I got the gas I drove home and the next morning I went to McDonalds which is only 5 miles from the house. As iI was sitting in line the engine light came on. I figured that the gas cap had not been put on properly,as I had the similar occurance with my work van which is a Chevrolet, and I took it to the mechanic and he checked it and the code came back saying that the gas cap was not on. He readjusted the gas cap and fixes the problem. But in order for the light to go off he did some steps to the ignition and gas pedal and it turned off the light immediately. With all that being said I readjusted the gas cap and turned on the ignition to see if the light would go off. It did not, so I called the On star center to get a diagnostics of my vehicle, and they said that it was emissions related concerning fuel leakage or somewhat. My question is , Is there some steps I need to try and get the light to go off, or should I take it in to the dealer? It is not driving no different nor am I having problems with jerking or stauling out. What should I do?