HowTo: Remove Notorious P0420 Code for less than a buck!
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Thread: HowTo: Remove Notorious P0420 Code for less than a buck!

  1. #1
    G20 Guru Helladank's Avatar
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    HowTo: Remove Notorious P0420 Code for less than a buck!

    So everybody (98.3% of people who have headers) knows the dreaded P0420 code!

    There have been numerous solutions this problem presented in the previous decade.

    Numero Uno: getting an o2 bung welded after the cat (* Definitely the most legit method (highly recommended if you want to get rid of the code and actually have a reading from your o2 sensor that will still be more or less consistent w/ ur stock setup ---> Possibly better for your fuel/air ratio if you do not have a piggy back, but I don't have a proof nor knowledge in the field.)) (Should run you bout $20 at an exhaust shop)

    2nd: o2 bung extender, I have heard that this works, but was unsuccessful in my attempt because the extender didn't fit correctly and would cause the o2 sensor to sit dangerously close to the front sway bar. (Should run no more than 7 bux)

    3rd: o2 Sensor simulators. There have been known to successfully get rid of the problem, at least the legit ones, but the universal one I got from o2simulators.com that was suppose to work according to a few other members got rid of my p0420 code only to cause the ecu to throw a P0138 (voltage to high blabla) And these are the only simulators I'm aware of that are still available new... will run you anywhere from $40-$50


    Now I recently stumbled upon a solution used on a maxima way back whenever... there is a detailed explanation of how this works on the thread I got the idea from(will be posted at the bottom for reference), and I'm guessing it functions essentially like the o2 simulator but for a ridiculous fraction of the cost and so easy a 3rd grader can do it....!!!!

    Step 1. Acquire resistor

    You need one 1.2K 1/2 watt resistor - you should be able to get them at your local electronics store or if you google them you will find countless options of where to get em...

    i.e. http://www.google.com/products?hl=en...-8&sa=N&tab=wf

    Step 2. Locate the o2 sensor signal wire

    Look at the wiring of the o2 sensor in the FSM for your year to make sure that the wire colors correspond, but typically the black wire on your o2 sensor will be the signal wire, this is the one you want!

    Step 3. Cut the sensor wire and solder/crimp the resistor in to the signal wire.

    Step 4. Tape it all up probably don't want to put tape over the resistor as it will get hot, but I did, and its been fine so far...dont ask why....

    Step 5. Clear the code, or disconnect the battery overnight, and pat yourself on the back because you got rid of that damn code for less than a buck.


    The code has been gone for weeks now and I doubt it's coming back but I will keep you posted if it does return. Although for less than a buck this really can't hurt to do if that's the only code keeping your service engine soon light on.

    Sorry no pics, but it's very easy and should only take 15 minutes.

    Source:

    Props to Danny 7633 for figuring this out.

    http://www.nissanclub.com/forums/f-q...p0420-fix.html
    Last edited by Helladank; May 04, 10 at 04:14 PM. Reason: partial OCD

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  3. #2
    G20 Newbie rmyc's Avatar
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    nice one, i might have to use it one day

  4. #3
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    so what did you do with the o2 sensor? is it still in the exhaust?im asking cuz mine is hanging ziptied to something under the hood.
    , you think frys electronics or circuit city would have it?

  5. #4
    G20 Guru Helladank's Avatar
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    Quote Originally Posted by polg20 View Post
    so what did you do with the o2 sensor? is it still in the exhaust?im asking cuz mine is hanging ziptied to something under the hood.
    , you think frys electronics or circuit city would have it?
    This is for the rear o2 sensor by the way.

    With this mod the o2 sensor is screwed into the down pipe and plugged into the stock harness just like normal, Most o2 sensors have three or four wires going from the o2 sensor to the plug adapter that plug to the stock harness, 1 of teh wires is your hot 12v wire, then you have 1 or two grounds(usually the same color) and finally the signal wire (the one you want--usually black).

    All you have to do is put the resistor in line with this wire.

    I'll post up a diagram later today when I get home.

  6. #5
    Dude, your bed is a car..
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    Quote Originally Posted by polg20 View Post
    so what did you do with the o2 sensor? is it still in the exhaust?im asking cuz mine is hanging ziptied to something under the hood.
    , you think frys electronics or circuit city would have it?
    make sure you cover the sensor from the elements or you will have to buy a new one after installing your cat back for emissions

  7. #6
    G20 Member bender-san's Avatar
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    I had been meaning to try this, but never came upon the opportunity to need it done. I'm glad to know that someone has successfully completed this mod.

  8. #7
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    Quote Originally Posted by Helladank View Post
    This is for the rear o2 sensor by the way.

    With this mod the o2 sensor is screwed into the down pipe and plugged into the stock harness just like normal, Most o2 sensors have three or four wires going from the o2 sensor to the plug adapter that plug to the stock harness, 1 of teh wires is your hot 12v wire, then you have 1 or two grounds(usually the same color) and finally the signal wire (the one you want--usually black).

    All you have to do is put the resistor in line with this wire.

    I'll post up a diagram later today when I get home.
    ok, so i would have to extand the wires on it to reach the rear 02 bung on the header or get another one welded in closer and then put in the resistor in.

    Quote Originally Posted by Cesardrgn View Post
    make sure you cover the sensor from the elements or you will have to buy a new one after installing your cat back for emissions
    its probably al messed up already but i will ductape it or something, the piping is not coming off for emissions.



    What i was getting at is, the sensor still has to be in the exhaust right, the resisistor is not gonna fix it when the sensor is just dangling under the hood.
    Last edited by polg20; May 05, 10 at 01:08 PM.

  9. #8
    G20 Member David SE-R's Avatar
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    That place is .29 cents but "Low order fee" is $7 & shipping is $9.28 for a grand total of $16.57. I think I'll try my local Radio Shack. Good fix.

  10. #9
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    Nice! I may have to do this if the pops up again. Don't ask me why, but I never relocated the O2 sensor. However I did get a bung welded (method 'Número Uno) but been too lazy to extend the wires!! I looked at that bung recently and yeah, not sure the rust on it will be easy to open it up! However, I think my ECU has given up throwing the code for me!!!

    As for that resistor, check your local Radio Shack or electonics shop. $16+ for s/h is ridiculous! There's also fleaBay.

  11. #10
    stock rocks! Robj80's Avatar
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    Dam I'm going to make an o2 wire extender cable and make a killing off you guys . I read at least once aday about someone needing to extend the wires.
    How do you know if LSD or not? Like you would check any tranny. Get down there and look for a bulge.

  12. #11
    G20 Guru Helladank's Avatar
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    Quote Originally Posted by Robj80 View Post
    Dam I'm going to make an o2 wire extender cable and make a killing off you guys . I read at least once aday about someone needing to extend the wires.
    Do it Rob, people will buy if its pnp!

    As for the rediculous shipping I didn't even see that...

    My local radioshack didn't have it, but a more legit electronics store had an 8 pack for like $1.29 Shit if I get bored I can probably put a stamp on a regular envelope and ship it out to you guys, I still have liek 6 extra...... but I'm guessing fry's might have it or any "legit" electronics store.

  13. #12
    Used to own a P10 thefultonhow's Avatar
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    Quote Originally Posted by Helladank View Post
    Numero Uno: getting an o2 bung welded after the cat (* Definitely the most legit method (highly recommended if you want to get rid of the code and actually have a reading from your o2 sensor that will still be more or less consistent w/ ur stock setup ---> Possibly better for your fuel/air ratio if you do not have a piggy back, but I don't have a proof nor knowledge in the field.)) (Should run you bout $20 at an exhaust shop)
    Quote Originally Posted by polg20 View Post
    so what did you do with the o2 sensor? is it still in the exhaust?im asking cuz mine is hanging ziptied to something under the hood.
    , you think frys electronics or circuit city would have it?
    Quick notes here. Keep in mind that there are two O2 sensors.

    The front one, attached before the cat (usually in the primaries if you're running stock exhaust manifold or SSAC headers) determines the air/fuel ratio. It's very important if you're running a stock ECU to NOT mess with this one. Piggybacks and Calum/JWT ECUs often cut this sensor out of the picture and use predefined maps, though.

    The second one, generally either after the cat or between the precats (in the exhaust manifold) and the cat, is solely there to determine catalytic converter function. The idea is that this one needs to have a different reading than the front one, or else the precat/cat isn't working right. It has absolutely no effect on anything except the CEL, for all practical purposes.

    The upshot of these facts:

    - If you have an O2 sensor "ziptied under your hood", that sounds like the front O2. The rear O2 would be ziptied near your front swaybar under the engine. It's acceptable to do this with the rear O2 (although not always effective). It's NOT acceptable to do this with your front O2 -- it may even prevent the car from going into open loop mode.

    - You don't need to do anything in particular to the rear O2 if you don't want to upset your ECU. The P0420 code has no bearing on anything the ECU does besides the codes it spits out. So if you live in a non-emissions region, you don't have to give a shit about it -- just go to Autozone to get your codes checked every few months to make sure another one doesn't pop up.

  14. #13
    G20 Guru Helladank's Avatar
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    Quote Originally Posted by thefultonhow View Post
    - You don't need to do anything in particular to the rear O2 if you don't want to upset your ECU. The P0420 code has no bearing on anything the ECU does besides the codes it spits out. So if you live in a non-emissions region, you don't have to give a shit about it -- just go to Autozone to get your codes checked every few months to make sure another one doesn't pop up.
    Some good points ^, but the whole point of this mod is to permanently clear the P0420 code, which is nice if that is the only code you have. Some benefits include not constantly having teh service light on your dash and not going to autozone frequently to make sure nothing else is wrong(they don't allow this in cali anymore some kind of lawsuit or something) or even if you have a scanner constantly checking your codes...

    This mod basically reduces the reading of the rear o2 sensor to roughly half of that of the front which is roughly what it should be if you had a normal functioning cat....

  15. #14
    brave little...
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    too much text in this thread.

  16. #15
    Used to own a P10 thefultonhow's Avatar
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    Quote Originally Posted by Helladank View Post
    Some good points ^, but the whole point of this mod is to permanently clear the P0420 code, which is nice if that is the only code you have. Some benefits include not constantly having teh service light on your dash and not going to autozone frequently to make sure nothing else is wrong(they don't allow this in cali anymore some kind of lawsuit or something) or even if you have a scanner constantly checking your codes...

    This mod basically reduces the reading of the rear o2 sensor to roughly half of that of the front which is roughly what it should be if you had a normal functioning cat....
    Absolutely. My point is more that having a completely non-functional and/or ziptied-up and/or improperly installed rear O2 will do nothing more than trip an annoying light and throw a code. This may or may not bother you and/or cause you to fail emissions, but it won't cause the car to function sub-optimally.

  17. #16
    Pining for "DMSentra" DMSentra's Avatar
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    Are you people really that cheap and care that little for the integrity of your G20 that you'll actually do this kind of tweakie crap? Pity the guy that buys your car next.

  18. #17
    G20 Guru Helladank's Avatar
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    Quote Originally Posted by DMSentra View Post
    Are you people really that cheap and care that little for the integrity of your G20 that you'll actually do this kind of tweakie crap? Pity the guy that buys your car next.
    Who said I was going to be selling my car, and if I did, I would probably bring it back to stock or sell to a forum member who would know every mod in and out. Aside from this, how does this mod make me cheap or lower the integrity of the G.

    This mod is simply an alternative to a pricey o2 simulator, the o2 extender, or simply running a downpipe/header and living w/ the P0420 code constantly on until your service engine soon light burns out.

  19. #18
    G20 Member bender-san's Avatar
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    Quote Originally Posted by DMSentra View Post
    Are you people really that cheap and care that little for the integrity of your G20 that you'll actually do this kind of tweakie crap? Pity the guy that buys your car next.
    Actually, no. Both of my G's (yes, now I actually have 2) are mechanically as sound as can be (minus the '95 needing a new antenna mast). I plan on eventually selling both of them and figured that it would be easier to get premium price if they were both as close to stock as possible. I was actually considering this mod for when my 99 NB Cal Spec Miata comes under the P0420 code since a new pre-cat/manifold is around $1,200. I have no plans on selling the NB unless some sucker shows up at my door with $25,000 burning a hole in his/her pocket.

  20. #19
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    will those o2 sensor spacers work in the rear spot? i was getting a rear o2 code but now i'm getting a 420 code
    Last edited by RIGHTAWAY; Nov 21, 11 at 06:04 PM.

  21. #20
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    should i just try to spacer first? is there a difference is o2 spacers?

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