Fault codes - advice please (again)

Appreciate that there are already many posts on these fault codes and I have looked but cannot really answer my question. Apologies in advance if I have missed the obvious - I will continue to look and update this thread if I get my answer.



Sooo - 2001 MGF non VVT - I am getting the engine management light on and 2 codes P0340 - Camshaft sensor a circuit Bank1 or single sensor - P0420 Catalyst system below threshold Bank1



Ok - I get the EML on usually after circa 20 miles of driving and it stays on throughout the journey. I can cancel the fault codes and the light goes out and stays out until I have do another 20miles and stays on again until codes cleared. Car seems to run well and good consumption figures.



My question is, if the camshft sensor is on the way out and throwing up a fault, is this likely to throw up the second fault, and what would you advise to change first.

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