Illumination of the Check Engine Light can be caused by a loose or worn gas cap.Google+
Car Problem Reports
Chevrolet Silverado 2500 HD Check Engine Light Due to Gas Cap Issue
Chevrolet Silverado 2500 HD Problem
Exhaust & Emissions Affected: Gasoline
Average Mileage: 80,658 mi (43,000 mi - 173,000 mi)
Visitor, 2006 Chevrolet Silverado 2500 HD, 86,000 mi
CHECK ENGINE LIGHT COMES ON THE IT SAYS TIGHTEN FUEL CAP ON THE DASH
Frustrated. I have a 2500HD 6.0 with 173,000 mile. Never a problem until now. The check engine light came on, so I had it diagnosed and the code said bad fuel cap. I also informed the mechanic that I don’t have any very little power at take-off. The mechanic said it could also be the catalytic converters are plugging up. I replaced the catalytic converters, which seemed to change the power issue. However, I still have the engine light stating a bad fuel cap. WTF. I removed the fuel cap and the truck starts and runs normal. However, now, when I fuel up the truck, it doesn’t want to start and it takes several cranks to start, and then it sounds flooded.
I don’t know where to start. The truck runs fine until I fuel it up, and then it takes several attempts to start the engine.
Visitor, 2006 Chevrolet Silverado 2500 HD, 43,242 mi
Check engine came on when engine was started . Did code check... it said evap problem . Gas cap o ring showed light wear . Installed new cap and cleared code ... check engine light off on restart.
Visitor, 2005 Chevrolet Silverado 2500 HD, 50,736 mi
gas cap turns engine light on...