I have a 52 plate Petrol Ford Focus and have the following error code:
P0420 Catalyst System Efficiency I understand this relates to either the O2 Sensors or the Catalytic converter. The car has 80,000 miles and has not been serviced for sometime. It only does short journeys. 10 miles a day.
What I would like to know is:-
1 How do I know if the Catalytic Converter is damaged or if it is one of the O2 sensors and how do I determine which sensor. The live data show that the sensors run at similar rates.
2. The sensor in Bank 1 is that the same fit as Bank 2 or do I have to buy a specific one for Bank 1 and 2
3. I have cleared the error the car is running fine should I see how it goes and will the light come back on if is the sensor or catalytic converter?
4. I have seen some cheap sensors on ebay but have read some horror stories about not fitting genuine parts what are your thoughts.
I need some expert advice.