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4thgenceli
09-03-2011, 07:34 PM
Fuck Murphy and his damn laws.

Here is the emission test history for our 2002 Mazda 626.

http://img.photobucket.com/albums/v488/celiman89/mazda.png

The 2007 test was no problem. Shortly after, the CEL came on. Throwing code P0421 (Warm up catalyst converter below threshold, bank 1). As we all know, this is either the cat converter or o2 sensors.

2009 test comes. CEL is on. I turn it off but missed the drive cycle and it failed (threw 'Not Ready' since the cycle wasn't completed). Blew some seafoam though it and it passed emissions.

2011 comes. Emissions are due again, and of course the engine light is on (same code). Not wanting to drop $300 on the new cat, I order up the new front and rear o2 sensors. Front one has to be shipped from warehouse. Ordered at 11am, parts come in at 2pm. I get the call that the part is in. I call up the wife to go pick them up and have them clear the CEL at teh same time (I was going to put them in the next day).

At that time, she says 'Oh the engine light is off'. She takes it to emissions and it passes. The next day, the engine light comes right back on with the same code.

So today I replaced the o2 sensors, and her car is running great right now again. Still shakes at idle, but we have a mount or two that needs replacing. Regardless....fuck murphy.

Eric Barrera
09-04-2011, 12:36 AM
The celica did that last time. Seems that cars don't like being plugged in to a government Computer... Go figure

4thgenceli
09-04-2011, 01:17 AM
Well the light came back on, but it's still driving better than before. Same code as before, but at least I know 100% it's the cat. It's about time for it to die. 185k miles :P

klapa
09-04-2011, 02:00 AM
I don't get why a cat would cost $300?

I don't have any ODBII cars - but can't you just buy a "generic" in-line cat?

Also - you don't need the California CAT - which always costs twice as much.

4thgenceli
09-04-2011, 02:31 AM
I don't get why a cat would cost $300?

I don't have any ODBII cars - but can't you just buy a "generic" in-line cat?

Also - you don't need the California CAT - which always costs twice as much.

Our mazda (2002 Mazda 626 2.0l LX) has two o2 sensors (upstream and downstream) and two cats. Upstream sensor hangs right off the exhaust manifold (like normal). After the manifold is the pre-cat, then the downstream o2 sensor then a 'generic' in-line. I'm sure Bruce has dealt with this engine code before also. It seems to be a common thing on the mazda 626. I read somewhere there may of been a TSB where the dealer flashes the ECU and lowers the sensitivty of the o2 sensor. Actually looks like Rock Auto has the direct fit pre-cat for around 200bux. Big box stores (CSK/etc) list it for around 300.

klapa
09-04-2011, 03:01 AM
Oh well - I feel you pain man.

If you have a young family then you need a newer type "ultimate dependable" car - so you must have something made after 1995.

I'm not in that boat - so I avoid ODBII cars like the plague - because even in NC - it doesn't matter what your actual emissions are - it just matters what that darn computer says.

And it always says the same thing - FEED ME! (with $$$)

Even so - sometimes I need my "Russian friend in the inspection business" - yet with an ODBII car - there is no faking it.

UtahSleeper
09-05-2011, 03:37 AM
I had that code on a protege of mine. I just gutted the pre cat and used spark plug anti foulers to pull the second sensor out of the stream a little.

4thgenceli
09-05-2011, 03:45 AM
I had that code on a protege of mine. I just gutted the pre cat and used spark plug anti foulers to pull the second sensor out of the stream a little.

Yep, that's the way to get around it.

alltracman78
09-05-2011, 03:57 AM
You wasted your money buying those O2 sensors. I still don't get why people waste money throwing O2 sensors at bad cats.
Cat codes [P0420, P0421] are always the cat. A bad O2 sensor CAN'T give the same signal a bad cat does.
"Sensitivity" of the O2 sensor has nothing to do with the code.

4thgenceli
09-05-2011, 05:02 AM
Agreed, but this thing is approaching 200k miles. We want it to run for another year or two before trading it in. Already noticed a better running engine with the new o2 sensors.

tuner4life
09-06-2011, 01:35 PM
My cars dont have to go through emissions. Therefore most of them don't have cats. hehehe

Facime
09-06-2011, 07:23 PM
Agreed, but this thing is approaching 200k miles. We want it to run for another year or two before trading it in. Already noticed a better running engine with the new o2 sensors.

uhhh...thats all in your head man since the downstream sensors do absolutely NOTHING in regards to fuel trim. They are an entirely passive sensor with the sole purpose of monitoring the cat.