Question

I have a 2001 Mazda Protege 2.0L with the engine codes P0131, P0421, & P0171, what could be the problem?

Answer 1

Hi there,

The P0421 code is causing the P0131 and the P0171. The converter right off the exhaust manifold is probably plugged up. This will cause the O2 sensor to not get a reading, and store the P0131 code, this will also blow exhaust gas back into the engine and cause the lean fuel mixture or P0171 code.

Answer 2

P0131 MAZDA Code - HO2S Circuit Low Input
Read more: https://www.autocodes.com/p0131_mazda.html

P0171 MAZDA Code - Lean Air/Fuel Ratio Bank 1
Read more: https://www.autocodes.com/p0171_mazda.html

P0421 MAZDA Code - Warm Up Catalyst System Right Efficiency Below Threshold
Read more: https://www.autocodes.com/p0421_mazda.html