Ford Focus 2003 Petrol 1.6
My car has been running rough for the best part of a year!! Finally it has thrown code P0420.
I have been told that this could relate to either a O2 Sensor or the CAT.
Would I not have another code apart from the P0420 if it was the O2 Sensor as code P0420 is Catalyst System Efficiency Below Threshold (Bank 1) which I would suggest is the CAT at fault?
Also I might be wrong but the car seems to run better now the code has been thrown up which I find very odd?
Any thoughts people?