So many codes...where to begin

['03 6 owner]

My 6 has 189,000 miles, and I've loved every one of them. However, I'm currently having issues. There are 4 codes showing; P0421 warm up catalyst below threshold (bank 1), P031 warm up catalyst below threshold (bank 2), P2227 barometric pressure CKT range/performance, and P0455 evap system leak (large). Replacing all 4 converters will cost me as much as a new car, so I'm trying to figure out which ones are bad, if the codes will tell that. I've been reading some of the threads trying to see if the codes tell which ones are bad, and can't see where they do. Replacing the O2 sensor would certainly be easier, but I'm guessing with that many miles, it is a converter issue. Three of the coils were replaced 2 years ago, but the other 3 are original. Performance issues are sporadic and right now it's running fine. The problem shows up as a drop in RPMs going from 40mph back to 60mph. It has backfired a couple of times, and I read that will kill a converter. So, I'm looking for advice....thanks.

 

[batou079]

sounds like sensor issues to me, although that should throw more of a specific code.
but hot damn, i think yours may be the highest mileage 6 i have seen thus far, must be a 2003 or 2004?

 

[zinger002]

sounds like sensor issues to me, although that should throw more of a specific code.
but hot damn, i think yours may be the highest mileage 6 i have seen thus far, must be a 2003 or 2004?

going to toss a guess at 03 based on his user name lol...

sounds like the heater circut for the O2 sensor, but the evap and baro throw me off and make me unsure. Have you tried contacting a mazda dealership?

 

['03 6 owner]

It is an 03. I took it to a local mechanic I trust because my experience with the dealers hasn't been all that great. The muffler shop I took it to said he could deal with the back two converters, but not the two bolted to the manifold. Those are the ones that will get expensive. I'm just trying to figure out if the codes are related to each other, and if they tell me which converters are bad.

 

[redspeed6]

Bank 1 and Bank 2 are the front cats (built in manifolds). Yes, they are pricey!
They are the first to go, more so if you have been misfiring and dumping raw fuel into a hot cat. O2 sensors on these 2 would be good to replace as well.
The evap leak could be a couple of things, large leaks usually mean gas cap loose or not sealing, purge solenoid stuck open, or your leak detection pump/vent is stuck open.
I would recommend your dealer do the evap leak testing, or if you mechanic has a smoke machine, he can use a scan tool to close the purge solenoid and vent in the evap system and also check your gas cap for leaks.
Not sure on the baro ckt, I don't remember seeing this code too many times, but I would make sure your PCM is up to date, there might have been a flash that takes care of this.

Need more info on the performance issues. Im guessing your fron 3 coils were replaced (easiest) and your back 3 (under your intake manifold) are the orginals.

 

['03 6 owner]

Here's where I am now. I've replaced the back two converters and the mass air flow sensor. The code it's setting right now is P2227. The problem is that usually has something to do with the EGR, but that doesn't affect performance, and mine is definitely affected. So, now it seems to be a try this and see if it works approach. Any ideas would be appreciated.

Thanks.