So, again, this OBD1 tool doesn't appear to have been reviewed before. If I ever get an MB S500 or other OBD2 Merc, I'll keep K6JRF's page handy. But then, his price for a list of codes is more than Rick's price for the list AND the tool. None of this is mysterious...a bulb and a switch is all that's needed to duplicate the functionality, and you can dig through the service manuals for the codes...it's the packaging that makes it worth a look.