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P0421 what do you think of this
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darom
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PostPosted: Tue Jan 17, 2012 4:36 pm    Post subject: Re: P0421 what do you think of this Reply with quote

(knocking on the wood) - installed 2 sets of anti-foulers on both banks, the code disappeared (P0421).

A question for CA owners with this mod: I don't remember the smog technicians checking underneath the van for the catalytic converters presence etc, however, will this mod create a visual inspection problem since we are modifying the original emissions equipment?

Thanks!

2002 Mazda MPV LX
1967 Camaro RS
1994 Dodge 2500 5.9L Cummins
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trogg1975
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PostPosted: Tue Aug 14, 2012 9:58 am    Post subject: Re: P0421 what do you think of this Reply with quote

Installed anti foulers at about 110K miles.......P0421 never returned......just over 180K miles now.......mayy have to replace someday as there is evidence of the AFs rusting.
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scross
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PostPosted: Tue Aug 14, 2012 11:21 am    Post subject: Re: P0421 what do you think of this Reply with quote

After much uproar and going back and forth, my city (a rather large one) has now decreed that you can fail OBD but pass tailpipe and still be golden. Hopefully this will turn into a national trend, thus requiring fewer solutions like the AF trick.
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helpmepassinpsectionlol
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PostPosted: Wed Aug 15, 2012 9:25 pm    Post subject: Re: P0421 what do you think of this Reply with quote

Hello Guys,

Have code p0421 (bank 1) appear, mechanic said to replace entire cat (should cost roughly 500$+ w/ labor) but after discovering about the non-foulers, i have cheaper way of fixing this and i am a week past inspection deadline so need this done asap.
So my question is, there is no way I can do this myself, i dont even have a drill to drill a hole in the non foulers, I wanted to buy them and just have on of the mechanics do it but does every mechanic know how to install one? can anyone recommend me someone in NY or NJ? I live on coney island Bklyn. If any of you help me, big bottle of grey goose on me!

thanks

P.s. 2003 mazda mpv about 75k miles
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drm7
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PostPosted: Sun Sep 14, 2014 5:15 pm    Post subject: Re: P0421 what do you think of this Reply with quote

As luck would have it, I got the P0431 code right before my annual inspection was due. P0431 is the same as the P0421 but on the opposite bank of cylinders. I reset the code and by the time I drove enough miles to complete the the code came back. I took the van to Mazda and they wanted $1,300 to replace the catalytic converter. After I picked myself up off the floor I found this post. I came back to report that after $4 in anti-fouling adapters, my code is gone and I passed inspection. The nice thing about the P0431 is that the O2 sensor is dead center of the van in the very front and bottom. You could likely do this without raising the van. I put it up on ramps anyway.

I've attached pictures to show the work.

2003 Mazda MPV LX - sage green, 4 seasons pkg, rear step, rear a/c, side airbags, roof rack, fog lights, traction control





IMG_20140831_153339.jpg

IMG_20140831_153339.jpg - File downloaded or viewed 1494 time(s)


IMG_20140831_155023.jpg

IMG_20140831_155023.jpg - File downloaded or viewed 1663 time(s)

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yongra
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PostPosted: Fri Jan 23, 2015 10:00 pm    Post subject: Re: P0421 what do you think of this Reply with quote

Did anyone got a code P0174 after installing doing this mod? I had the tubes put in about a week ago and no CEL so far. But, I checked with my OBC reader and it has P0174 code pending.

Thanks,
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drm7
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PostPosted: Sat Jan 24, 2015 8:58 am    Post subject: Re: P0421 what do you think of this Reply with quote

It has been 4 months since I did this and I've not had any other code.
2003 Mazda MPV LX - sage green, 4 seasons pkg, rear step, rear a/c, side airbags, roof rack, fog lights, traction control
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yongra
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PostPosted: Wed Apr 22, 2015 11:54 pm    Post subject: Re: P0421 what do you think of this Reply with quote

Found out what the problem was. I had a torn intake rubber hose after the air filter. That was causing the lean mixture since MAF sensor could not control the air flow.

After it was fixed, no CEL. This fix works.

Thanks for posting.
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tedburt
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PostPosted: Mon Sep 07, 2015 3:41 pm    Post subject: Re: P0421 what do you think of this Reply with quote

I'm the owner of a 2002 MPV w/ 176K. The van failed the emissions part of the annual NH vehicle inspection. Was faced with a $2400 estimate to replace both warm-up cats (PO421, 431). Briefly entertained the thought of an experiment to see if MPV's can float. Instead, opted for the anti-fouler fix, which my kids called "Dad's voodoo magic van repair". IT WORKED! CEL went off, stayed off, no pending codes. 800 miles later, still off! Not sure what principle of physics is at work, but it got my van thru the miserable emissions inspection. Thanks!
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scross
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PostPosted: Mon Sep 07, 2015 5:59 pm    Post subject: Re: P0421 what do you think of this Reply with quote

The "principle of physics" here is that with the downstream oxygen sensor in its normal position, it reads relatively little difference between the oxygen level behavior coming out of the cat (which it monitors) vs. that going into the cat (which is monitored by the upstream oxygen sensor), thereby indicating to the engine computer that the catalytic converter isn't doing its job. (A properly operating converter will cause a noticeable difference here - but if the cat wasn't there at all, or wasn't functioning at all, then the two readings would be practically identical.) By moving the downstream sensor out of its normal position with the anti-fouler trick, that sensor now gives different readings (inaccurate readings, of course, but that's what you want for this scenario), which the engine computer then interprets as a properly functioning converter.
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Thul
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PostPosted: Sat Jan 02, 2016 9:09 am    Post subject: Re: P0421 what do you think of this Reply with quote

Will this trick work if cat 2 is clogged? If so I will try because I have codes 171 and 174 on my 04 mpv. As it stands right now I ready to perhaps clean the catalytic converter after I changed my coil bank one with code 301.
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novalight
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PostPosted: Mon Jan 04, 2016 1:38 am    Post subject: Re: P0421 what do you think of this Reply with quote

u can always buy aftermarket unless u live in commiefornia
2004 A-spec Touring Edition (look it up)
instagram: Tangofury
Added Suspension: Carbing Tower Bar, TEIN Stechs, Airlift Airbags, Energy Suspension Bushings
Added Exhaust: Cherry BOMB Glasspack, 22" X 3" TIP
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CaptnKC
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PostPosted: Tue Jan 26, 2016 6:00 am    Post subject: Re: P0421 what do you think of this Reply with quote

I have a 2002 Mazda MPV LX, When I picked it up it had 102,000 miles on it. It sat idle in a field for about 2 years in Western PA, and the moisture and snow got to the exhaust system.

The 2002 Mazda MPV has 4 catalytic converters in the front. You may want to look at those in addition to changing the O2 sensors.

I could not do the work myself, and the Mazda Dealer wanted $3100+ to repair the cats and the O2 sensors. I purchased all my exhaust parts from Advanced and AutoZone and found an independent shop to do the repairs. The parts cost approximately $700, and the installation cost approximately $1500.

Catalytic Converters: http://shop.advanceautoparts.com/c3/catalytic-converter/15311

O2 Sensors: http://shop.advanceautoparts.com/c3/oxygen-sensors/16466?isAllVehicle=false&showTitle=&vehicleIdFromReq=453450&vehicleIdSearch=453450

Repair Pal list the following:
Fault Code Definition
Code P0421 is triggered when the Bank 1 Warm Up Catalytic Converter's emissions reducing efficiency has fallen below the minimum allowable threshold.

Symptoms

Check Engine Light will illuminate
In many cases, no abnormal symptoms may be noticed
In some cases, there may be a noticeable lack of engine power
Common Problems That Trigger the P0421 Code

Defective Warm Up Catalytic Converter
Engine misfires have damaged the Catalytic Converter
Common Misdiagnoses

Oxygen Sensor(s) are replaced when the real problem is a damaged Warm Up Catalyst
Warm Up Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
Warm Up Catalyst is replaced when a misfiring engine is the real problem

My Mazda MPV also has new brakes, Struts and Shocks, new Radiator, and one plug and coil with 129,000 miles.

I suggest you purchase an Actron Analyzer from Advanced or AutoZone to do your own diagnostics occasionally. Please also make sure that you close the gas cap tightly when you refuel. You may get a check engine light if you don't because the EVAP System is not closed. Idea
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CaptnKC
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Thul
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PostPosted: Tue Jan 26, 2016 10:04 am    Post subject: Re: P0421 what do you think of this Reply with quote

I am appreciate all of the info. I am wondering if is my valve cover is leaking oil , because I felt oil behind the rear ignition coils. I really hope this does the trick
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frehours
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PostPosted: Thu Apr 27, 2017 1:22 pm    Post subject: Re: P0421 what do you think of this Reply with quote

A sharp emissions inspector would spot this,
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