Thanks for the OBD clairification. It's my wife's car and I checked last night, definitely only OBD1. I think I am getting the idea of the code reader. I have another dumb question. If I read the code using the LED/button that is on the diagnostic connection block what will I be reading? Or another way to ask, what is the difference with the code reader that I need to build and use for each pin and the codes that will come from the already in place button/LED on the pin block? For the homemade code reading device, which pins should I 'read'. All of them?

In response to the wiring question, I am not really sure what I am looking for (or where) for wiring problems. I would guess I do have problems based on the fact that everyone seems to have this eventually for this vintage car. We've never had a performance symptom of it only the light coming on. I've looked at the wiring on the top left of the motor area and the insulation seems cracked but no bare wires anywhere I can tell. What a pain in the neck, how does this crap happen with all the research that goes into this stuff!!

I also have a 93 300D and I have to say the diesel seems much simpler all things considered (and it sounds so much nicer to drive). I wish I had two of these rather than one and the gasser!