This problem arose several years back when the check engine light came on. The mechanic informed me that the oxygen sensors were frozen in place and would be costly to repair. My state does not check exhaust emissions so I decided I would live with the problem. Then it occurred to me to try cleaning the engine. So I started putting Lucas engine cleaner in with every gas refill, and, low and behold, the check engine light went out. If I forget to put Lucas engine cleaner in with a gas refill the check engine light will come back on again after several miles. The light goes off again on its own after installing the Lucas engine cleaner.