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Cat. Converter and CEL

I have a CEL and it reads P0431 (bank 2 warm up cat converter problem). The car is a 2003 Mazda MPV with 110 k miles and it previously had trouble with ignition coils, which seemed to be due in part to oil leakage into the spark plug wells (some oil was visible on the ig. coils). The engine runs great but it looks like I might need to replace the cat. converter. I’ve read that this will be very expensive (~$1000) but I’ve also read that I can replace it with a high-flow magneflow converter for about 100 bucks. What do you guys think? O2 sensor?

I would NEVER spend $1000 to make a light go off…The light can stay on forever as long as the vehicle gets me where I want to go…

Can’t get the car inspected with the light on. Plus it’s my wife’s car and I don’t want her to be left stranded.

My manual doesn’t have P0431 (it’s not a Mazda FSM) The codes for cat efficiency are P0420 and P0432 …I don’t know why it includes the “warm up” notation there. It gives you the impression that the heater circuit on the 02 sensor may be faulty.

I’ve looked at several forums on this topic. They had this problem on earlier units and it was a faulty rear 02 sensor that triggered the code.

Essentially your catalyst is an oxygen storage medium. When you’re lean, the catalyst is soaking up excess 02, when you’re rich, it’s consuming it in the reaction with the excess hydro-carbons. The front 02 reads the lean:rich conditions …and the rear one should see a, more or less, steady state. Once it starts reading the same reading as the front sensor, only separated by a slight delay, the cat is deemed inert and needs replacing.

If you’re creative and want to cheat, construct an extension harness and move both pre-cat REAR O2 sensors below the main cat. It will never see the problem

Keep in mind that that code means the computer detected unexpected data from a sensor. That could be due to a sensor, the item the sensor was monitoring, a wire etc. Trouble shoot before replacing.