I have a 1998 Chevy K1500 with the 305. I got this code the other morning. I had someone check it with scanner, and this is the code I got. I was not adding any gas at the time, so the cap was not off. The truck was running at a gas station, I was in getting my morning newspaper. Went to leave and the "service engine soon" light came on. This is what google say it is: This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine. I got the light cleared, check the cap, make sure it was on tight. Drove for about 150 miles and the light came back on. Pretty sure it is the same problem. Has anyone had a problem like this? and is there anything else I should look for?? Thanks Dan My plan is to replace the cap, remove some rust that is on the filler neck and reset the computer again.