Yesterday I was driving my Mazda Millenia S '99 when I saw the check engine light is on. I connected it to the computer and I got a code P0421- warm up catalist below threshold. I previously noticed a gasoline smell in my car and I don't know if it has anything to that code. I checked the code online and it said there can either be a problem with oxygen sensors or catalystic converter. Did anyone ever have that problem before? What do you think it is, the catalyst or sensors? Please help,I have an inspection coming up!!!!!!!!!!!!!!!!!!

 

I have the same problem in my millenia and i also can smell gasoline, especially after starting engine.
So far haven't found a reason.

 

you may have 2 different problems. however, if raw gas is being squirted into the combustion chamber(s), that will destroy the pre cats(P0421/31) quickly. they will clog up, and overheat, and then all kinds of other problems will arise. so, in order to properly fix this, you must first find out about the gas smell, if it is squirting into the combustion chamber, just changing the precat will only make the new part die, too. raw gas also kills oxygen sensors.

 

how can I tell which problem do I have? do what can I do if the problem is indeed the raw gas being squirted into the combustion chamber(s)?