I have a 2014 c250 with over 220k miles . I notice it over cranks n it sounds like a diesel . Swaped out the cam sensors to bosch still same issue ended swaping out camshaft adjuster still doing the same thing checked the harness for any damaged wire nothing its just that one code i get P0340 permanent

 

How does the car run? "Permanent" codes are not current problems and will eventually self-delete if the problem has been fixed. If the status is not "current", then you have probably fixed the problem.

https://www.bar.ca.gov/industry/pdtc...%20scan%20tool.

 

I did a little searching around and came across this post. May be the timing chain tensioner and timing chain adjuster. I just skimmed through it so not really sure. May send you in the right direction.

https://mbworld.org/forums/c-class-c...-guidance.html

 

The car runs fine no issues at al driving just starting up