1992 964 " ! " warning light showing

Vehicle Information: Year: 1992; Body Type: Convertible; Total Mileage: 30,500;

I took my cab. to the only local P dealership because the "!" keeps popping up in routine driving. They told me the clock had a short in in and they fixed it. Three days later the clock still doesn't work (It doesn't really matter) but the "!" still comes up. The car just had its 30,000 service. It runs very well, but the thought that something is amiss concerns me. The fluid levels are fine, and nothing else seems to be malfunctioning. Sometimes I seem to smell a sulfur smell. Car doesn't miss, starts immediately and idles perfect. Any clues? I really appreciate the job you are doing on this site.ThanksLar92 Porsche72 Pantera01 Prowler