Ford Fiesta engine management light on

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.


Source: http://www.obd-codes.com/p0420

so p0420 could be cat replaced or just a sensor or both?

it could be the cat or it could be a lambda ideally you need to get the live data read via computor to see what the engine is doing

how much about would fords charge for this