P0421 - mazda

Question

Just had catalytic converter and downstream 02 sensor replaced and vehicle is still spitting out same p0421 code. Not sure what to do now?

Answer 1

Hi there,

This car has 2 converters. One is right off the exhaust manifold and is called a Pre cat. This code is for that converter. If the one under the car was replaced, then it was the wrong one and it will need to have the correct one replaced to resolve the issue.