Dare I say it?
Three days and counting, I think my tech found the problem. It was the S16/3 starter lockout and reversing lamp switch (with selector lever position recognition), also called the safety neutral switch. It is an electro-mechanical switch that is actuated by the shifter and sends gear selection information to the EACM, more properly called the EA/CC/ISC module, as I have learned. Part no. M000-545-62-06, $69.00. It showed up on the diagnostic unit as a misread on the shift lever position, that would not represent actual gearshift selector changes. Apparently that was enough to kick it into 'limp home' mode. I got my car back Friday and drove it 45 miles - no problems. I drove it 20 miles Saturday - no problems. I gave it the dreaded car wash test Sunday - no problems. I just might start enjoying this thing again! Wish me luck!
1995 E320 Wagon Moonstone Grey/Parchment 106K mi.
2007 E63 AMG Graphite/designo 75K mi