i know that this topic was hit in the install of headers thing but i tried to get help on that thread and no one replied... it seems to me that when/if people resolved their CEL problem they kept the solution to themselves... i got the megan racing header and i installed it and got no CEL for about 30 miles... after that the CEL came on and i had the defouler thing standing by to rid my self of said problem... well put that on there reset the ECU and 30 miles later it came on again. so if anyone has any ideas on what i may have done wrong or any suggestions on how to fix this please let me in on it before i go and do something drastic...

see i got frustrated and went and got my DVOM. i took a few measurements and this is what i came up with... so its a 5v circuit and essentially the first sensor reads x amount of voltage based on harmful particles in the exhaust... then its supposed to pass through the cat and the sensor afterwards is supposed to read significantly less harmful particles... well what would happen if i just cut the sending wire on the lower 02 sensor and wired in like a 2.5 v resistor or something... that way it couldnt read more the 2.5 volts and thus shouldnt trip the sensor right? i know that most original ideas have already been done by someone else so if i'm on to something that someone else has done please let me know and give me pointers cause i am just shooting in the dark... oh yeah and how much are new sensors if i screw this up?

there is a possibility that you could have damaged an o2 sensor too. If you have a dealer that won't wince at mods and stuff, I'd have them see if it's damaged or not. If it is, this could be the reason for your CEL.

Also, you can try adding 1 more antifouler to further extend the o2 sensor from the exhaust stream (although it'll be a tight squeeze)

the 02 sensor is fine... if it was damaged it wouldnt have read voltage on min/max of my DVOM. i suppose i could try adding another anti fouler... though the emmissions guy i talked to said that that doesnt even make sense and its not gonna do anything.

i have the same problem... the dealer said my o2 sensor was broken but why would my cel come on after like 80 miles?

Did you use 2 anitfoulers or just 1? I used both that came in a pack, drilled one out with a half inch bit and screwed the o2 sensor in that one, then screwed the whole thing into the second one with the small hole. Put that in the bung, plugged it in and cel went off within minutes.

yeah i used 2... and when i first fired it up no CEL then exactly 30 miles later it popped on so... im more asking opinion on the new idea and if anyone knows if this CEL will put the car in "limp mode"

Yes it does go into limp mode, runs rich, and has been dyno tested to show a loss in power. Not sure why the antifouler works for some, but not others. Mabey altitude and climate plays a role, or your sensor could just be fried.

There's a guy on here who has the same problem, and bought a generic obdII scanner and leaves it plugged in all the time so when the cel pops up it reads it and deletes it right away, not ideal but it works.

Anyhow, good luck.

Antifoulers or the 02 sim did not work for me. I had to relocate the secondary o2 sensor behind the cat in the midpipe and no cel ever again. I spents weeks with trial and error with the antifoulers and some tc's won't accept that as a fix.

Resistors are not measured in voltage. So there is not 2.5v resistor. The resist current flow, thus dropping voltage. So you would have to know how much current you are dealing with, and in this case that would not be the most accurate setup if it worked at all. But, if you get enough measurements at different times (a diagnostic tool would work well logging the two sensors together) you could most likely get a good idea of the relationship between the two and create a simple voltage simulator to wire in place of the 02 sensor. I dont have the header, but maybe I can take time to look at the voltage relationship and come up with something.

And constantly clearing the code does nothing for the issue, just keeps it from "b!tching" at you.

I will see if I have time to hook up to mine this weekend and see what it will take to make a decent simulator. I think there may be one available for the tC if I remember correctly. But it seems I heard it was a bit spendy. Due to being busy lately I cant promise how soon I can look at it, but I will post something if I figure it out.

i need it im getting 220 miles to the tank !

idn about what your saying 2 antifoulers...... i bought mine of of clubsciontc.com it had 2 peices but they screwed together..no drilling..

well so far what i have both read and heard from word of mouth is that yes there is a limp mode... but i believe that the degree to which you say is inaccurate... the only limp mode i was able to scrounge up was something about not being able to rev past like 3000... and as far as a solution i think i pretty much got it but would love input on what yall think... as far as the sensor having jack and or crap to do with tuning the engines performance i havent found anything... as far as i can tell all it does is tell you when your cat is done. so a theory that me and a few others have cooked up over the last day is to chop the sending wire and put in a varying potentiometer... that way all i have to do is turn the dial (so to speak) until it provides enough resistance to turn off the CEL... CEL goes away so does the "limp mode" that i honestly havent even noticed yet. so what do yall think... it sounds pretty simple to me, and we all know that its never that simple so does anyone have any reasons why this wouldnt work?

i need it im getting 220 miles to the tank !

idn about what your saying 2 antifoulers...... i bought mine of of clubsciontc.com it had 2 peices but they screwed together..no drilling..

If you go to AutoZone, they come two to a package by a brand called HELP! The hole on the male end of the adapter is too small for the o2 sensor to thread in properly, that's why you would need to drill it out. The other hole remains small, reducing the amount of exhaust gasses that reaches the sensor at its extended position.

It is a voltage dependent signal. not current. This means little current should be flowing in the circuit, so using a resistor is not the most accurate fix if it works at all.

look i think your gettin hung up on verbage... i'm not an electrical guru... my experience with electrical anything is very limited... what i do know is that there is a way to limit voltage output in a circuit... whether it be some sort of diode or what ever i dont know. when i said resistor it was because that was pretty much the only word that i could think of to get my point accross. obviously you know more than i on this electrical stuff so you tell me what kind of parts i need to do this. my idea is real simple. its a 5v circuit. the sensor up top reads 5v because its gettin exhaust right out of the block. the sensor down below (seeing as how the cat is no longer there) is reading 5v now as well. i figure alls i gotta do is put something in the circuit that will limit that sensors ability to send a signal higher than say 2.5 volts or so. i know its doable. i just dont know what kind of part i need. if you do then let me know what i need and i'll tell you how it goes.

Not trying to argue, just trying to help. I am hooking up to mine in about 30 min while I run errands and will log the two 02 voltages. I will have a better idea of what is needed after that, and may even build one if I have some extra time. The best case scenario is to simulate the approximate relationship between the two sensors using a variable voltage source (for this case an adjustable 5V regulator IC and control circuit would be pretty simple). If I actually starting making them I would probably work to use an A/D convertor matched to a programmable IC and a D/A output. Basically, a circuit that can be re-calibrated for different applications.

But the basic need is something with a variable voltage output that is based off the input from the first 02. The absolute most simple fix would be if a steady voltage can be found that will still keep things under spec. For example, if you could feed a constant voltage that would keep it under spec you would avoid the 02 simply.

As far as the circuit, while fed with a 5V signal, 02 sensors typically output in a range of 0 - 1V. The output of the 1st 02 sensor is typically sweeping back and forth around 500 mV or 600mV or so, withe the second sweeping around about 500mV, but travelling a smaller distance on either side.

and somewhere around the first line you went greek.... i appreciate the help but can you keep it more simple for the idiots... :loser: im not that smart. and obviously you are. so what you're saying is that there really is no simple solution. so if you were to make said thing and could prove that it would work... how much would you charge someone like me for it. and could i get some kind of break on cost cause i stirred the pot on the idea. i only started thinking this cause the defouler thing doesnt work 100% because it doesnt make sense... my understanding of that is that the 02 sensors dont read the amount of air but the content of the air in the pipe. so it shouldnt matter how much air it gets just whats in the air.

so i have the wrong anti fouler? you want me to go 2 pepboys? i bought the one for the headers.. from clubscion tc ..

idn whats wrong any one have a slubscion tc antifouler and have never got a check engine light?

im wasting so much gas!

The front o2 sensor is a 0-5 volt sensor and the rear o2 sensor is a 0-1v sensor. You can read up on various Toyota o2 sensors here http://www.autoshop101.com/forms/h37.pdf. I hope this can help a little.

Funny, they didnt include the 1st 02 sensor in ghe generic data for the obdII data, which is very suprising to me. Only the second one shows up on my diagnostic tool, which reads the generic data. In any case, during a fairly normal drive I got some log data yesterday. The 2nd 02 sensor scales almost its full range during normal driving, which kind of shoots down the "simple" possible fix I had :P On some cars, both sensors are 0-1v sensors. For example, on my saturn, the first sensor reads nearly full scale back and forth, while the second stays within about 30mV of 500mV. So if that was our case I would say to try simply applying about a .5V signal in its place. Then see if the ECU was smart enough to know that was not normal.

On ours though, my bet is that the ECU is smart enough to know that the second one is not reading correctly, because its readings arent changing over time.

I plan on getting the Toyota specific data for my scan tool. If I do I will look at it again.. or I will if I get a header soon. :P

so i have the wrong anti fouler? you want me to go 2 pepboys? i bought the one for the headers.. from clubscion tc ..

idn whats wrong any one have a slubscion tc antifouler and have never got a check engine light?

im wasting so much gas!

The one from ClubsciontC is the correct one and is drilled out, I've had mine on for over a year and 10k miles and no cel. If the code your throwing is the P0420 code then it shouldn't have anything to do with your MPG.

Well at my dealer told me my sensor was broken, but maybe they got that code because of the headers.... i get 220 Mpg every tank flooring it alot... i need it fixed if im loosing hp.

From what I understand the P0420 code is for a "malfuctioning Cat" Letting you know that you need to get it fixed. I don't see how or why the ECU would richen or retard timing, since the catyaltic convertor has nothing to do with fuel mixture or timing.

Did you use 2 anitfoulers or just 1? I used both that came in a pack, drilled one out with a half inch bit and screwed the o2 sensor in that one, then screwed the whole thing into the second one with the small hole. Put that in the bung, plugged it in and cel went off within minutes.



yeah, use two......that is what i did.

watching....woulb be nice if you could do the "simple fix"....possibly use a +.5V source from the car itself, and send that to the ECU...

does the O2 have one or two wires....if it's two, could it possibly be a variable resistor? that would make sense as to how much voltage it readds....just oopens and closes with the exhaust gases....if so, couldn't one replace it with a smalle potentiometer to reduce the voltage output returned to the engine?

i sure hope so.....but if i am wrong, alas, on to a more expensive fix

so im just getting a little light? but what if my sensor is brokenlike they said??

flooring it alot...

Maybe lay off if it a little. I know that sounds dumb but give it a try on a tank and see what it will do.

My understanding of the function of the downstream (after cat) 02 sensor in an OBD car was to monitor catalytic converter efficiency. The upstream like engifineer said should sweep from .3vdc to about .7vdc after the engine has reached normal operating temperature and switched to closed loop operation because the exhaust gases have not travelled through the cat yet. The downstream will remain flatter with less fluctuation due to the catalytic converter doing it's job.

That's what I remember from engine performance (efi) class and here's what I found online. Once again, YMMV.
http://www.aa1car.com/library/ic50234.htm

JOe

Also, which o2 sensor eliminator are you using?

anti-fouler from clubsciontc.com

anti-fouler from clubsciontc.com i try not flooring it but i live in miami andi get tryed so much.. it like impossible for me..

so let them try you and wave them off

anyone have any more ideas?

ive had my cel on for about 12 k miles since i got my aw header i installed the antifolers still cel.. dealer ship told me a while back my sensor was broken.. i thought mayb they said that cuz they didnt understand i was missing a cat .

well 2 days ago i got my bodykit installed i leave the shop with the cel on and about 60 miles later it just turns off. and sudenly i get about 60 miles more to
the tank with same the same kinda driving style~


and i checked my cel led since i changed them to blue to c if it was the ledt hat went out but no..

what just happend?

good Questions :eyebrow:

its hard to tell...

ive had my cel on for about 12 k miles since i got my aw header i installed the antifolers still cel.. dealer ship told me a while back my sensor was broken.. i thought mayb they said that cuz they didnt understand i was missing a cat .

well 2 days ago i got my bodykit installed i leave the shop with the cel on and about 60 miles later it just turns off. and sudenly i get about 60 miles more to
the tank with same the same kinda driving style~

what just happend?

same thing happened to me, after 3 months of driving my CEL randomly went off. as far as my gas mileage, i think it got worse with my CEL off, but i've got nothing to prove it.

the thing that confuses me though is when the CEL is on, the car is supposed to be in "limp mode". but my car pulled harder noticeably harder with the CEL ON. can anyone explain why this might be happening? or is has this happened to anyone else

limp in mode will limit your transmission an normally not allow you to run past 2nd gear or a certain rpm depending on what type of transmission you have, o2 sensor so far that i have heard, has not caused a car to go into limp in mode.

limp in mode is really just a seafety featur to protect what ever components that are left from serious catastrophic damage, while still allowing you to get to the closest available shop. Your o2 sensor monitors your exhaust gases and will let your computer know if the fuel trim is running too rich or lean or just right. if it is running too rich or too lean it usually meants that something id being overcompensated for and getting too much fuel or too little fuel.

If you have the antifoulers and are still throwing a cel here is a good (FREE if you still have the stock exhaust manifold) fix.
1. Knock the catalyst out of the manifold. It will come out in big chunks.
2. Take your two antifoulers apart.
3. Cut a piece of catalyst to fit in the antifouler. Be careful not to make it to thick or you will smash it when you screw the two antifoulers together.
4. Install back into car.
5. Reset check engine light.
6. No more cel.
**This modification is only necessary if you already have the antifoulers installed and are throwing a cel**

I have had to do this in a couple of different vehicles where the antifoulers did not work. I have yet to have any cels after doing this. I can not guarantee that it will work for everyone else but for the cost it is worth a try.

clubsciontc.com is a site w/ a good antifouler price and product?