2014 VW Tiguan P0303 CODE
P0303 code # 3 cyl misfire, replaced all spark plugs and the # 3 coil. Still have
the check engine light and it won't reset, even if I disconnect the battery. So
A reset doesn't fix the problem. A misfire can be caused by poor spark, but it can be caused by fuel or mechanical problems, as well. Might be the plug wire, a clogged/defective injector, pulse problem at that injector, or a loss of compression in that cylinder. Have a mechanic check this.
If the problem has been fixed the light will go off in a few days. Or you can clear the computer with a scan tool or code reader. As you found out disconnecting the battery on an OBD II vehicle will do nothing! Hope that helps! Jim