How To: Make Your Own Rear O2 Simulator for $5

[Robb235]

Just curious why you would use a 250V capacitor on a 5V circuit? Was that just the only one they happen to have in stock at radio shack? A 5V or even 10V capacitor would be plenty for this application.



Also just FIY for anyone interested in doing this to your O2 sensor: the specific rating of the capacitor/resistor isn't what allows this circuit to work; the key is to match the capacitor/resistor to each other so the transient response of the RC circuit has the appropriate time constant. In this case a time constant of 1 second appears to do the trick. So any RC pair with a 1 second time constant will function the same. (i.e. 1µF/1MΩ, or 1mF/1kΩ, etc)

Sounds like you know more about the "how it works" than I do. I didn't come up with this mod myself, I've just seen write-ups for it on different sites. Since many of us suffer from the dreaded P0420 code on our 4Runners, I figured I'd try it here, make a post about how I did it, and share my results.

 

[MTD]

Just curious why you would use a 250V capacitor on a 5V circuit? Was that just the only one they happen to have in stock at radio shack? A 5V or even 10V capacitor would be plenty for this application.

Also just FIY for anyone interested in doing this to your O2 sensor: the specific rating of the capacitor/resistor isn't what allows this circuit to work; the key is to match the capacitor/resistor to each other so the transient response of the RC circuit has the appropriate time constant. In this case a time constant of 1 second appears to do the trick. So any RC pair with a 1 second time constant will function the same. (i.e. 1µF/1MΩ, or 1mF/1kΩ, etc)

Darn EE's and their RC circiut and time constant witchcraft!

 

[broken wrench]

Best bet if you don't live in Cali, stay clear of the vehicles. We tell our buyers not to buy them. They rarely accept aftermarket cats and when they do your on barrowed time. You can try what we call an 02 bung or spacer, it doesn't delete it but moves it out of the stream enough to clear code in most cases.

In Tx having a missing cat can lead to the state not letting you register your vehicle and fining you. An inspector letting it pass safety can get a fine and suspension of license's driving and inspector. Even diesels are stamping codes on the valve covers as to what cats are factory equipped.

But as we all know it easy to get an inspectors license with little to no knowledge of vehicle mechanics. Thus resulting in high turn over of inspectors due to officers randomly running sting ops for lax inspectors.

I hope this make it mo better for grammar and English lit folks, I was only able to attain electronics and mechanical eng degree's. I hated English !!!!

 

[MTD]

In Tx we have a missing cat can lead to state not letting you register vehicle and fines. An inspector letting it go gets fine and suspension up to loss of license driving and inspector. Even diesels are stamping codes on valve cover as to what cats are factory equipped.

But as we know it easy to get an inspector license and most have no knowledge of vehicle mechanics. Thus a high turn over due to officers randomly inspector sting ops.

might want to reread these last two paragraphs for grammar mistakes. They got kind of hard to follow.

 

[Doc2012]

might want to reread these last two paragraphs for grammar mistakes. They got kind of hard to follow.

Might want to re-read all this for mistakes.

Best bet if you don't live in Cali, stay clear of the vehicles. We tell our buyers not to buy them. They rarely accept aftermarket cats and when they do your on barrowed time. You can try what we call an 02 bung or spacer, it doesn't delete it but moves it out of the stream enough to clear code in most cases.

In Tx we have a missing cat can lead to state not letting you register vehicle and fines. An inspector letting it go gets fine and suspension up to loss of license driving and inspector. Even diesels are stamping codes on valve cover as to what cats are factory equipped.

But as we know it easy to get an inspector license and most have no knowledge of vehicle mechanics. Thus a high turn over due to officers randomly inspector sting ops.

There are plenty of people here that have used an aftermarket cat, have passed inspection, and have been fine for years, if this was the route they chose to go.

If you live in Cali, I would say to stary clear, simply because Cali does the Sniffer test, and while the light might not be on, the exhaust can still cause it to fail, from my understanding (I don't live in Cali, nor whould I ever want to).

A O2 "spacer" is going to move it out of the gasses? How? Hose gasses are still going to be surrounding the O2 sensor. those gasses are going to fill every inch of that tail pipe, so by moving the sensor "out of the stream", you're really just moving the sensor up. Not doing anything at all really.....

 

[broken wrench]

might want to reread these last two paragraphs for grammar mistakes. They got kind of hard to follow.

I see them, with two junior techs to train. It's hard to type, look and listen without wanting to hit yourself with a blunt object when it's over 100 degrees

 

[broken wrench]

Might want to re-read all this for mistakes.





There are plenty of people here that have used an aftermarket cat, have passed inspection, and have been fine for years, if this was the route they chose to go.

If you live in Cali, I would say to stary clear, simply because Cali does the Sniffer test, and while the light might not be on, the exhaust can still cause it to fail, from my understanding (I don't live in Cali, nor whould I ever want to).

A O2 "spacer" is going to move it out of the gasses? How? Hose gasses are still going to be surrounding the O2 sensor. those gasses are going to fill every inch of that tail pipe, so by moving the sensor "out of the stream", you're really just moving the sensor up. Not doing anything at all really.....

I see it first hand, majority of cali cars do not pass with aftermarket cats.So we use a dealer cat based on vin and all is good. We do use aftermarket cats on all types of vehicles. Yes, they do pass. We do the sniffer test here.

As you stated, it is a spacer moving it out of the stream enough for the 02 to fall into calibration peram's. Most of the time it is a weak or failing sensor by a small %, so it does work. Until the sensor completely fails.

And so the great debate continues on which is the best method to fix or work around the 02 sensor codes.

 

[MTD]

I see them, with two junior techs to train. It's hard to type, look and listen without wanting to hit yourself with a blunt object when it's over 100 degrees

hahaha :whip: keep them in line lol

 

[MTD]

Might want to re-read all this for mistakes.

Meh :tsk:

 

[Robb235]

A O2 "spacer" is going to move it out of the gasses? How? Hose gasses are still going to be surrounding the O2 sensor. those gasses are going to fill every inch of that tail pipe, so by moving the sensor "out of the stream", you're really just moving the sensor up. Not doing anything at all really.....

I've heard of this before. People typically use spark plug non-foulers that you can find in the Help! section of Autozone. Most 3rd gen 4Runners can't use this method because we have the bolt on oxygen sensor, not the screw on type.

 

[Nelsonmd]

Darn EE's and their RC circiut and time constant witchcraft!

So simple division is witchcraft you say? I think UW might want to take back your permission to use their logo as your avatar:doh:

Might want to re-read all this for mistakes.





There are plenty of people here that have used an aftermarket cat, have passed inspection, and have been fine for years, if this was the route they chose to go.

If you live in Cali, I would say to stary clear, simply because Cali does the Sniffer test, and while the light might not be on, the exhaust can still cause it to fail, from my understanding (I don't live in Cali, nor whould I ever want to).

A O2 "spacer" is going to move it out of the gasses? How? Hose gasses are still going to be surrounding the O2 sensor. those gasses are going to fill every inch of that tail pipe, so by moving the sensor "out of the stream", you're really just moving the sensor up. Not doing anything at all really.....

You're right about the Cali test, though I think that the aftermarket CAT's are getting a bit better and may pass the sniffer test now. I believe that Walker CAT's are actually on the approved list. Others have said that in Cali they actually check the model/brand of CAT you installed and it has to be an officially approved one (i.e. that CAT company has donated to the campaign fund for some Cali rep...).

You're incorrect about the spacer doing nothing. The O2 sensor is designed to have the sensing element right in the middle of the exhaust flow, so if you take it out of the exhaust flow, then you are getting less gas blowing through/by the sensor, so less detection. There is a huge difference between flowing gas and stagnant gas (from a sensing standpoint). If it worked the same in stagnant gas, then believe me, they would not go through the trouble of making the sensor stick out into the middle of the ridiculously hot and corrosive exhaust gas.

 

[midcoma]

FWIW, here's my experience.

A while ago, probably 3-4yrs, I had an exhaust related engine code on my Tacoma. I don't remember exactly which code. I followed the procedure in post 1 to modify my rear O2 sensor and the CEL went off and the code cleared.

A couple months ago I got a CEL with the code of P0137 - Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2). I decided to buy a new Denso O2 sensor and the URD simulator (I gutted my CAT and welded a straight pipe through it a while ago). After switching the modified O2 sensor for a new one with URD's simulator, the CEL and engine code went away.

So does the modified O2 sensor work? Yes, but for how long.
Is a modified O2 sensor exactly the same as a URD simulator? Probably not.

 

[jeremyc74]

So simple division is witchcraft you say? .

There's a little more to it than that.

 

[MTD]

So simple division is witchcraft you say? I think UW might want to take back your permission to use their logo as your avatar:doh:

ound: JK

 

[MTD]

There's a little more to it than that.

Meh.

 

[cashmoney]

And that is why I quit math at Algebra 2. Math shouldn't have letters in it!!

 

[Nelsonmd]

There's a little more to it than that.

Not if you reduce it by limiting the time constant to what you actually want it to be (apparently about 1s in this case) and the voltage to the fixed supply oltage of the sensor. once you do that, the equation for time constant is only related to the ratio of R and C, so if you know what ratio you need, then it really is just as easy as simple division.

Always reduce the problem to the least complex solution. :humble:

 

[ToyTaco]

Hey guys, I'm about to do this mod on my 02 taco. I need the help of some electrical gurus. I'm in Canada and radio shack is no more. I went to the local electrical store told the guy what I needed by cross referencing the radio shack part numbers the capacitor he gave me is TOPMAY 105j250v and the resistors are 1/2 watt 1m OHM 2%, the radio shack says 5%, Can you guys tell me if this will jive if all wired in properly? Thanks guys

 

[TheDurk]

Hey guys, I'm about to do this mod on my 02 taco. I need the help of some electrical gurus. I'm in Canada and radio shack is no more. I went to the local electrical store told the guy what I needed by cross referencing the radio shack part numbers the capacitor he gave me is TOPMAY 105j250v and the resistors are 1/2 watt 1m OHM 2%, the radio shack says 5%, Can you guys tell me if this will jive if all wired in properly? Thanks guys

The capacitor info you gave does not include the capacitance--so it might be right or not. The resistor is fine. 2%/5% is the tolerance and either is fine for this application, and 2% is better than 5%.

 

[ToyTaco]

Thanks Dirk. I searched 105j it says that is the code for 1uf.