What can cause P0421?

The most likely failure that causes this code is the Catalytic Converter, but oftentimes the Catalytic Converter can fail due to the engine running poorly. Always make sure the engine is running properly before replacing the Catalytic Converter.

How do you warm up a catalytic converter?

A very elegant method to speed the warm-up is the use of the engine itself as a “preheater” for the catalytic converters. High exhaust gas enthalpy to raise exhaust system mass up to its operating temperature is obtained by the use of extreme spark retard, stochiometric mixtures, and fully opened throttle.

What happens when 02 sensor goes out?

If your vehicle has a bad oxygen sensor, it could run irregularly or sound rough when it idles. A faulty oxygen sensor can impact your engine’s timing, combustion intervals, and other essential functions. You could also notice stalling or slow acceleration.

How do you fix a p0421 code on a Mazda?

Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0421 code is combined with other codes, try fixing the other codes first. The cost to diagnose the P0421 MAZDA code is 1.0 hour of labor.

What does the p0421 code on a Honda Accord mean?

The P0421 code is set when the Engine Control Module (ECM) detects rear HO2S value difference becomes closer to value of front HO2S. The ECM monitors when vehicle speed is 25-60 MPH, load is 22-45 percent and engine speed is 1000-3000 RPM.

What does the p0421 code on a catalytic converter mean?

As the code description implies the P0421 code means that the vehicle’s control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting).