Illumination of the Check Engine Light can be caused by a loose or worn gas cap.Google+
Car Problem Reports
Chevrolet Tahoe Check Engine Light Due to Gas Cap Issue
Chevrolet Tahoe Problem
Average Mileage: 91,755 mi (16,000 mi - 150,000 mi)
Visitor, 2007 Chevrolet Tahoe, 41,075 mi
Tahoe does not get driven much as you can see only 41075 miles now check engine light is on and goodyear said it is fuel system not pressurized correctly. ???
Visitor, 2007 Chevrolet Tahoe, 150,000 mi
Check engine light came on gave a code that there was a minor emission system leak.
Visitor, 2007 Chevrolet Tahoe, 16,000 mi
I repeated had the check engine light come on after I bought my truck (used w/ 16000mi). This took 8 trips to the dealer before they figured out it was a fuel line issue. The metal receiver for the gas cap wouldn't secure properly. Since it was a used car when I bought it I couldn't do the normal lemon law suit. I was able to sue for breach of contract and had GM award me money for the time & effort of 8 trips to the dealer and missed work hours.