My wife's 2001 e320 was at the detailers, and the shifter failed. She got it to me in limp mode, and I have been working the problem. I replaced the brake switch during the troubleshooting process, so the plunger now lets it shift out of park normally. This morning I took the shifter assembly out of my 2000 ML55AMG, put it in the e320. It did not fit exactly, but it enabled me to do a test drive, and it shifted fine. It was out of limp mode. I completely disassembled the old shifter, cleaned all the electrical parts, and reassembled it. Now the car will not start. When I turn the key, the dash lights come on, but no starter. I remembered that when the car first failed at the detailer, she told me that it would not start, then called me back and said that they had gotten it started, but had to use the button to get it into drive. Is there some trick that I am missing?
I am totally stumped.

Follow-up. I tried disconnecting the battery for a while, did not work. After I got the shifter back on, I put the OBD2 meter on, and got no faults, which is new. Up to now, I have always gotten the PRND switch fault before. I checked the linkage to the transmission to be sure it was in park, and the brake switch.

Another update- I tried my ML55 shifter again, and the car starts and runs great. At this point, I am positive that the problem is the three circuit boards in the shifter. Either the rheostat that indicates shift position, or two other boards that are housed in the shifter. Is it possible to buy those boards seperately? and why will it not even go into limp mode anymore?