Hi Guys Right this post is going to be a challenge and probably a lengthly one but I really need all your help. I saved up to buy a mercedes S class w221 because I've always wanted one and found a 2009 S320 CDI on gumtree which had been in a crash (front drivers side) and been repaired, it was a good price but he said the conductor plate in the gearbox needed replacing because the TCU was faulty. So I researched online on how to replace this part and from the videos I watched it seemed to be quite strait forward, he said it was drivable and so I traveled 200 miles to go and view it and it seemed to be in mint condition and started and drove quite well apart from when you stopped you had to put it in park and then back into drive otherwise it seemed really sluggish to cycle trough the first few gears, so I thought this was ok and would make it back to my house. I drove it all the way back without any problem UNTIL..... I got home and turned the car off but then it wouldn't start again ???? after quite a few tries it started but once turned off has not started again since !. I am quite mechanically minded and have rebuilt a few engines in the past and fixed/service all of my cars for the last 15 years but this has lost me!! at first I thought maybe the battery was the culprit but nope, then replaced the starter motor but nothing (I have another post with a video regarding this starting issue). I ended up deciding to buy a star diagnostic system, it arrived and a few errors were present one of which was a module under the dash drivers side wasn't communicating correctly or wasn't married up to the ecu correctly, and I'm sure I read somewhere if you replace this module it will start the car 40 times but only this many until installed correctly, also the error for the tcu was saying it cannot communicate with the ecu....So before I attended to these problems I decided to pull the dash out and reinstall it because it wasn't fitted correctly at all by the previous mechanic and there was airbag errors and I wanted to also check he had installed and connected all these correctly, all went well until I asked a mate to give me a hand over the weekend to reinstall it all, was going well until I went to get some grub for us and he plugged the white plug with the black and white wires which goes into the bottom of the cd/dvd unit into the INSTRUMENT cluster !! and turned the ingnition on ?!?!?! anyway I got back and he explained what he had done because he couldn't find the correct wire which went into the back of the instument cluster and that was the only one that fitted !?!?! Grrrrrrr I immidiately dissmissed him from helping me and installed the rest myself and now the navigation screen does not light up steering wheel does not respond, gear shifter does not respond or change onscreen like it did before and none of the buttons in the middle of the two screens dont work either ??? :-( I am gutted with all this and desperately need help and advise, I asked a local Mercedes garage to sort it out for me and he refused to touch it or even look at it, said he has been stung by these W221's before and wont go near them again ?!?!?