Find the error code. The previous owner proyknew about this problem. Thats why you found an extra shifter in the boot. Its probably the reason that car was garaged for a long time and the mice made a home in it.I did change speed sensors
Some days it's fine so maybe a short?
/\ /\ /\ Exactly this !! Very likely a simple fault, but if you just keep guessing you may never fix it !!drive it to a mechanic with an SDS. You cant fight an invisible enemy.
I have one. It can talk to the transmission. It helped me fix a problem once. After knowing what SDS can do, I wish I added 400 or more so to the 150usd I paid and I would have gotten myself an SDS.What about a icarsoft MB 2 scanner for Mercedes?