Question

2000 Mazda Protege 1.8L with code p0420 what could cause this code?

Answer 1

Hi there

This code is for the catalytic below threshold. Basically it means the converter is no longer cleaning the exhaust like it should. In most cases the converter has to be replaced to resolve the problem. Sometimes if you have an exhaust leak or a bad rear O2 sensor will cause this code.

Answer 2

P0420 MAZDA - Catalyst System Efficiency Below Threshold Bank 1

Read more: https://www.autocodes.com/p0420_mazda.html