After the "check engine" light was on for several days, I took the car in for service. Since it appeared that the gas cap was the culprit, it was tightened and the light went away...that is until I purchased more gasoline, when the light reappeared. The gas cap was then replaced with a new one, but that didn't work either. The idea was to isolate the inexpensive possibility. Finally, the nitrogen smoke machine was used and a leak was found atop the fuel tank around the fuel pump module. The smoke machine is costly, but no where near as costly as removing the fuel tank to install a new module. However, considering the potential of a fuel delivery failure and possible fire hazard while far away from home, it was more comforting to have the problem resolved. Thanks to the technician and D.J.