Hello, 

 

I have a fiesta Mk6 1.4 zetec 2003 and I recently got a check engine light. I plugged in a cheap obd scanner and it read off the code p0420 catalyst code. 

I cleared the code once to see what happens and it didn't come back on for a while. When I put my foot down hard to go up a steep hill for example or rev high for a set time it will come on. 

I cleared it to reproduce it and again. It comes up only when the car revs highly for a certain amount of time. Like going up hills that are steep. I once forgot to drop a gear and went up a hill in fifth gear. It made it but the light came on again stating catalyst fault.

Anyone got any ideas on what's wrong with it and what my next steps should be I have had standard maintenance done like spark plugs, coils, coil plugs etc. Not sure on an engine tune up like valves etc as I only had the car since July. 

Any help would be great. 

Thanks all

Ryan

Have you checked the wiring of the O2 sensor, might need a new cat though - what were the emissions on the MOT last time?