Originally Posted by tjts1

The C320 I bought a few weeks ago had this exact problem. Its actually the reason I bought it. P0715 is generated by the TCM (transmission computer) and can't be cleared by a conventional OBD2 code reader. Normally you would have to take this to a dealer and hook it up to a star diagnostic tool in order to clear the code and bring it out of limp home mode.

I used an icarsoft i980 to clear the code from the TCM and it immediately shifted beautifully. The previous owner of my C320 did the same thing you did. Had the conductor plate and plug replaced at great expense only to find the transmission wouldn't come out of limp mode At this point the shop was telling him the whole transmission needs to be replaced so he gave up and sold the car to me.

The icarsoft can talk to all of the car's computers and clear all the MB specific codes. Since you have a W211 theres another version called icarsoft MBII which can also deal with the SBC brakes on your W211. For this problem either the i980 or the MBII will fix this issue. IMHO the MBII would be a better investment for the w211. Theres a ton of info and videos out there about both devices.