Hi Jocko124

The fault that your getting involves the speed sensor on the transmission conductor plate.

If your transmission is in permanent limp mode then then the Transmission Control Unit (TCU) needs to be reset (fault cleared) with the Mercedes Star Diagnostics tool. The errors are reported up to the ECU and can be cleared from the ECU, but they're held in the TCU and must be cleared from there or the transmission won't come out of limp mode.

As to why your car has gone into limp mode in the first place, I'm not sure. Especially when it was going fine to start with. I don't think the problem is with the TCU or the solenoids, but are you certain you've installed the conductor plate properly (as the speed sensor can be bent up a bit sometimes when you get them out of the packaging)?

However, it all might be fine now that you've replaced the conductor plate again, but you won't know until you clear the fault from the TCU and go for a drive.