Hello karen-- I would say that the check engine light on your 1994 Mercedes-Benz S320 is trying to tell you something. What it doesn't tell you is what the problem is. If your car were a human, the check engine light would be the headache and there could be numerous causes, like a cold, or the flu, or a brain tumor that will kill you in a week. I would advise you have a reliable mechanic hook up your car to a computer and see what codes come up, thus diagnosing the problem. It could be as simple as a filter or a sensor or it could be a complex problem. I would think you would want to find out soon with such a nice car. Good luck from Bovan.