[2012 C250]

Don't know if anyone is experienced enough here to diagnose this over the net:

Had a P0304 code and a pending P0303 code that went away after the spark plugs were changed and the shaking that was happening to the car went away after the spark plug change but the P0304 code still remains even after swapping the ignition coils, not sure what is going on since the car drives fine. 


Is there something still wrong with my car or am I using the wrong OBD scanner to reset the check engine light.



It could be the scanner that you are using. If the problem no longer exists it should reset after a few driving cycles. Typically within a week.

Let us know if that doesn't work.

The check engine light went away a couple of days ago but last night I lost a lot of engine power and the check engine light came on.  I restarted the car and the check engine light went away and the car was driving normally again.  I checked with my OBD scanner even though there is no check engine light and I am now pulling codes PO304 again and PO303 (pending).  Should I swap out ignition coils or is this a bigger problem?

Sure you can do that but I would start by installing new spark plugs unless they were recently done. 

I changed the spark plugs already a couple of weeks ago.  The check engine light is not on but I'm still wondering why those codes are being pulled and the car drives fine except for that hiccup two nights ago where I lost like 25% power to the engine till I restarted the car (the check engine light was on during that time for a couple minutes till I restarted the car).  Also I've noticed the triptronic manual gear shifting stopped working as well but no check engine light is on right now.


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