code p0421 and p0421

[anusemoon]

what do these codes mean.....
p0421 and p0421 ( warm up catalyst efficency below threshold ( bank 1 and 2 ) 98 millenia failed emission test how can i fix this???

[anusemoon]

P0421 and P0431

[dsatt12]

That's not very nice... now I had to go learn all about Miller cycle engines.

As for your question, there are lots of Mazda boards I found with info on this. You need to check with your dealer and see if your Millennia needs the PCM reflashed (they'll run your vin# and check). This is purported to fix 80-90% of the P0421 codes. Beyond that, you've either got a bad catalytic convertor or bad O2 sensors it sounds like.

Now hope your supercharger doesn't go out on you to the tune of $7000 for a new one. I thought Auroras were bad...