"Check Gas Cap" Warning
For a number of months the "Check Gas Cap" warning message appears randomly followed shortly by the "Service Engine" light. It does not appear to be related to gas fill-uos, in fact occurring days and hundreds of miles after a fill-up. My mechanic scanned for error codes and came up only with a generic evaporative system code. Investigation of the system did not find any leaks or other obvious problems. I can clear the Gas Cap warning by disconnecting the battery for a few minutes but the service engine light stays on and finally goes out many days later. What are the chances it really is the gas cap? It is always tightened with many clicks at fill up and is never loose when the warning appears. If not the cap what else should we be looking for? The car is a 2002 Seville SLS with 85000 miles on the odometer.