Engine light of my AUDI A4 is still bright, I used Autosnap CR800 Code Reader to check, the fault code is P0303, my question is if it continues, what situation will appear ?

 

dont let it go, that code should be a cylinder #3 miisfire. if you let it go you can ruin your catalytic converter among other things. check for bad coils, spark plugs, fuel injector or wiring to either the fuel injector or coil.