P0420 Ford - focus 2004 p0420

Question

the o2 sensor was coming up as the problem about a week ago and now all it says is p0420 catalyst system efficiency below threshold bank 1. would fixing the o2 sensor fix the problem?

Answer 1

Hi there,

Depending on the original code, it is possible. If the O2 sensor is calling for the wrong fuel mixture then it might be running to rich which in turn can cause the P0420 code.