I have been posting this a couple of times and I have also been to steve b's site on the DIY section but I have not been able to decipher exactly how you would proceed on reading the codes on a 87 420SEL? I have read about grounding this wire and connecting that wire to a positive! I am new to owning a MBZ and I do not want to screw this up and make more problems for myself, can any tell me how to read these codes with a multi meter and HOW to read them after I retrieve them I have a code listing from the BAT tech site but that only pertains to 190 and 300 models. I realize that I am beating a dead horse but I have searched all the threads pertaining to fault codes and not ONE says anything about the w126 or do all the 126's of this era have the same procedures for retrieving the codes? I am at wits end with this rough idle at the stop light while in gear and it only occurs after the car has warmed up, this is other wise an awesome car, I know we have techs on this board and I would really appreciate all the info and direction that I can. RECAP:

1. Is there a check engine light?
2. Exactly how do I retreive the codes with a multi-meter?
3 where is the plug located at?
4. Am I looking for cycles,waves, numbers on the MM?
5. am I looking for the little round thing on the drivers side fender?

Last but not least:

THANK YOU ALL