I have 2 codes that showed up on my reader for 2000 Volks Jetta 2.0:
P0303 and P1255
I know the list of potential problems but am unsure which code to address first. I would also like to know if both codes are related and can point to the area where I need to start. The check engine light is on and it's running running extremely rough with a strong smell (catalytic converter).
Should I be checking spark plugs first for code P0303 or start with addressing the Short to ground problem (p1255)
Any help is appreciated.