All,

I ended up with Code 19 as the reason for my now-working (another story) CEL. That usually means a new ECU - very expensive fix. A guy named Joey on the Technical Help forum at Mercedes-Benz Club of America F0RUMS gave me a great lead: see Jim. I then checked with JImF who had an engineered solution that avoids putting in a new ECU. He's at http://pages.prodigy.net/jforgione/MB_S500.html. His replacement E-PROMs are programmed identically to those in the newer ECUs from Mercedes, and contain the software fix for the adaptation limits. These limits were too tight in the earlier ECUs and are usually the cause of the Check Engine Light being turned on by Code 19. The dealer would charge $2200 plus installation. Jim's E-PROM is in the $60 range, and the longest part of the install is driving to a tool dealer for the proper Torx bits (if you can, bring the ECU with you to ensure you get the right sizes). It's a doggone miracle!

Alan Case
87 300E (for sale on eBay)
94 E420