How to cure Cel/Mil from removing cat with Non-Fouler

i don't believe so...

still no p0421 code for me
although i am getting p0300 code but that was after i installed my second motor... Still can't figure out whats causing the random misfires
 
i don't believe so...

still no p0421 code for me
although i am getting p0300 code but that was after i installed my second motor... Still can't figure out whats causing the random misfires

I had the same code recently and replaced the plugs and cables as advised by my mechanic and the issue was still there. Then came to find out one of the ignition coils was bad and replaced that and its all good.

I also just installed a new header in my p5 and after about 20 miles the cel was triggered. I'm here finding my solution and will be hooking it up right tomorrow. Will this pass emissions testing? I sure hope so.:)

Saweet

If its a little raspy check if its coming from where the header meets the mid pipe, If the header pipe pertrudes the O gasket on the end of the header you need to grab a sawzall or hack saw and make it flush, also use a torque wrench to tighten the bolts right (To the block with the torque wrench, & compress the springs a bit where it connects to the mid pipe, but if there is any bit of pertruding of the header past the O gasket, its most likely going to make raspy noise), there is no more bracket holding the header to the engine and it moves ALOT if not tightened right the raspyness gets louder and louder.
I stopped at Salvo when I went for my cruise after finishing up today I heard some clacking coming from the underneath were the header bolts to the main cat and was thinking..damn thats not good! Thanks to RacerX I believe I know the problem. I love you guys!(headbang)
 
Hello to all my fellow forum members. I have a 2.0L 2001 protege ES manual with 97000 miles on it right now. For the last 3 months or so, I have been throwing a P0421 code every now and then. I assume my pre-cat was going bad. I kinda ignored it. Can't remember the code number, but I have a new code which refers to the 2nd O2 going bad.
Wanted to do the non-fouler trick to get rid of the P0421 code. Questions is will the non-fouler work with a bad O2 sensor? Also, assuming that the O2 wasn't bad, will that eliminate the P0421 code with a bad pre-cat? I ask this because I know most of you who use this trick is because of a header installation... Has anyone used this trick for a bad pre-cat? Thanks for any insight.
 
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hey does anybody know the recent part number for this? i tried the part number given but it didnt come up as anything, i was at autozone but he was using the parts exchange thing and nothing came up

plus this is over 2 years old,

edit: nevermind looked it up on napas website and its still the same part number, i guess autozone just doesnt have the right stuff
 
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2.5 Millenium

haha...VERY nice write up man!!! great pics too

Wondering if you can help me out with the placement of the non fouler set up on my 2.5 V6 Millenium S. My error code is PO420 - catalyst efficiency below threshold Bank 1. This is a California setup where the pre cat is not attached to the manifold but, is under the floorboard. My understanding is that Bank 1 is closest to the firewall. Do I place the modified O2 sensor in front of the pre cat or behind it? My guess is behind (or maybe it's on the pre cat itself). Please note that my objective is to pass smog (not fun in CA), install a new universal pre cat (high flow if it's appropriate) in its place and save a grand in the process.
Thanks for any help or suggestions you can give me.
Oh, and the reason I'm not taking any chances with the pre cat is that I blew a Ford 351 Cleveland motor in my RV ten years back because of a clogged cat. The CEL didn't come on at all and it ended up costing me over 4 grand. Some people on this thread seem to think that there's an inherent problem with the ECM "falsely indicates an emission concern" I'm not sure I want to take that chance. I'd respect your opinion on this if you have time to reply on this as well.
Thanks again, and if there's a special charity that I can donate $50 in your name, give me that info as well.
 
Wondering if you can help me out with the placement of the non fouler set up on my 2.5 V6 Millenium S.

(hmm)err, umm, I had the same problem on my Prolege and my Tribune, but my RS-8 never had that problem. What kind of car do you drive?

I apologize in advance
 
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Wondering if you can help me out with the placement of the non fouler set up on my 2.5 V6 Millenium S. My error code is PO420 - catalyst efficiency below threshold Bank 1. This is a California setup where the pre cat is not attached to the manifold but, is under the floorboard. My understanding is that Bank 1 is closest to the firewall. Do I place the modified O2 sensor in front of the pre cat or behind it? My guess is behind (or maybe it's on the pre cat itself). Please note that my objective is to pass smog (not fun in CA), install a new universal pre cat (high flow if it's appropriate) in its place and save a grand in the process.
Thanks for any help or suggestions you can give me.
Oh, and the reason I'm not taking any chances with the pre cat is that I blew a Ford 351 Cleveland motor in my RV ten years back because of a clogged cat. The CEL didn't come on at all and it ended up costing me over 4 grand. Some people on this thread seem to think that there's an inherent problem with the ECM "falsely indicates an emission concern" I'm not sure I want to take that chance. I'd respect your opinion on this if you have time to reply on this as well.
Thanks again, and if there's a special charity that I can donate $50 in your name, give me that info as well.

It sounds like you do have to replace an O2 sensor and it sounds like it is the sensor before your pre cat. I don't understand what you said; do you have a pre cat on your car? I know I had a similar issue in my protege 5 but I did have 2 error codes that came down to needing to replace the pre cat and also had to replace an O2 sensor. If you only have this single code then it sounds like it is just the O2 sensor and if you have a modified system with no pre cat then it may be the sensor after the pre cat location that is causing the code. If you look it up and find that bank 1 is the first O2 sensor in the series then I would replace it and you should be good to go. It doesn't sound like you have any other problems with your car but if you do still have the pre cat hooked up that may be getting dirty and may need to be replaced soon. You will get an error code should that happen and your Mazda has a much better or at least newer engine than that old Ford 351. Back then information about what your car is doing wasn't so available for the driver but these days the cars let you know pretty quickly.
 
im going to have to try this out this week when i get my new exhaust.
 
I did installed my header with this today but on my drive home, my CEL still ended up coming on. Reset it when I got home. I'll have to see if it comes back tomorrow.
 
The codes pulled are
P0140 - 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0037 Rear HO2S heater control circuit low ON 2 HO2S heater

What do you think?
 

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