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

[Nelsonmd]

I replaced my rear O2 sensor a couple weekends ago, which meant that I no longer have the mod in place. I did it just to see if both my cats were really bad, or if my rear sensor was just worn out. My CEL popped on not long after, pretty much indicating that my cats are not operating at the efficiency level that the ECU would like. My wife threw away the old O2 sensor with capacitor and resistor still attached thinking that it was junk, so I'll be making another trip to Radio Shack to redo the modification.

Well, you still haven't figured out if your cats are bad, you could still have an exhaust leak. Any of the mods done to stop a P0420 code will mask both an exhaust leak or a bad CAT I think.

Have to given a full inspection of your CATs? It was pretty easy for me to lay underneath with the engine running and move my hand around the flange joints to see if I could feel a warm air leak. Pretty easy to find. Do that before you make any decisions on how to solve this.

 

[Robb235]

Well, you still haven't figured out if your cats are bad, you could still have an exhaust leak. Any of the mods done to stop a P0420 code will mask both an exhaust leak or a bad CAT I think.



Have to given a full inspection of your CATs? It was pretty easy for me to lay underneath with the engine running and move my hand around the flange joints to see if I could feel a warm air leak. Pretty easy to find. Do that before you make any decisions on how to solve this.

Seems like a moot point when I can just put the resistor and capacitor back to make the P0420 go away.

 

[Nelsonmd]

Seems like a moot point when I can just put the resistor and capacitor back to make the P0420 go away.

Maybe for you if GA/TN doesn't do inspections and you are willing to risk getting caught, but for anyone reading this thread from Cali or other states, it's not a moot point at all. No post here is really just for the OP, others read them too.

Plus, alot of people actually want to fix their vehicle, not spoof it. That's not criticism of your decision to spoof it, it's just what alot of people here prefer.

 

[Robb235]

Maybe for you if GA/TN doesn't do inspections and you are willing to risk getting caught, but for anyone reading this thread from Cali or other states, it's not a moot point at all. No post here is really just for the OP, others read them too.

TN has inspections in certain cities (just took my wife's 2012 Civic through a couple months ago. GA does also. Last time I went through inspection they checked to see if my vehicle had a catalytic converter present, checked with OBD2 reader to make sure no codes were found, and then hooked something up to my gas tank in place of the gas cap to check what I can only assume is the EVAP stuff. I imagine most other states do something similar.

Plus, alot of people actually want to fix their vehicle, not spoof it. That's not criticism of your decision to spoof it, it's just what alot of people here prefer.

BS. Judging by how many threads ask about how to fix the P0420 code without dropping a small fortune on new cats, we both know that's a false statement.

 

[Nelsonmd]

TN has inspections in certain cities (just took my wife's 2012 Civic through a couple months ago. GA does also. Last time I went through inspection they checked to see if my vehicle had a catalytic converter present, checked with OBD2 reader to make sure no codes were found, and then hooked something up to my gas tank in place of the gas cap to check what I can only assume is the EVAP stuff. I imagine most other states do something similar.

Yeah, so they may not notice the extra bit of "fat" on your O2 sensor wrapped in electrical tape, but if the inspector is alert, they easily could notice it. Here in MA they don't typically get under and look at it, they just check the OBD2 port (though I try to go to the laziest inspectors so that they don't get under and check, because I think they are supposed to).

BS. Judging by how many threads ask about how to fix the P0420 code without dropping a small fortune on new cats, we both know that's a false statement.

Ok, it's not BS, read those threads again. Most of those guys not wanting to drop a fortune on their cats are not opposed to replacing the CAT with aftermarket ones for under $300 for the set ($150 for 49 state). In the last couple years I have seen a pretty good number of guys use aftermarket CAT's and post up here that it took care of their P0420 code. When I first got my 4runner back in 09, I couldn't find any records of people positively saying "XXXX brand aftermarket cats took care of my P0420 code", but there were a couple people that explained that the OBD2 system standards for the emissions were pretty high, and aftermarket (non-platinum) CAT's may not be able to achieve sufficient efficiency to turn off the OBD2 code. There wasn't a clear solution other than "illegal for on-road use" simulators or forking over for OEM cats that was guaranteed to solve the P0420 problem (or had a good track record).

Of all the threads about that I have seen, the majority of them seem to be deciding to go with aftermarket CAT's, not the URD sim, or the $5 sim that has been out on the internet for years. And 1 or 2 I can think of went to a muffler shop and got an exhaust leak fixed, which was my point. I don't know how you can call my comment BS when it is demonstrably true. Yeah $5 is cheap, but I haven't seen anyone choose that route in a very long time.

I hope you aren't interpreting my posts as criticism of your method. That method has been around for years, and seems to work pretty well, no dissing it as a workaround. The URD sim offers something a bit more, if no more than an (expensive) environmentally protected package and plug and play simplicity. I feel confident in saying that the vast majority of the old timers here would recommend figuring out the actual problem before slapping on a band-aid if for no other reason than to know what you're dealing with.

 

[Jon]

:uzi::gun4: op2:

Count me in! I'll play this game for $10. As for the cat, just keep the damn thing. This is not a performance engine, it's built for economy. Sorry to burst anyones bubble but it's not like you see the amazing 3.4 being swapped into anything going down a drag strip or anywhere near any track. That would be the 2JZGTE.

 

[Nelsonmd]

:uzi::gun4: op2:

Count me in! I'll play this game for $10. As for the cat, just keep the damn thing. This is not a performance engine, it's built for economy. Sorry to burst anyones bubble but it's not like you see the amazing 3.4 being swapped into anything going down a drag strip or anywhere near any track. That would be the 2JZGTE.

Yeah, I'm with you. I kept it as long as I could, snuck my way through a couple inspections, then just stopped getting inspected for 4 years. Then all of a sudden I got 2 tickets for it in 2 days and had to get it to pass inspection.

 

[Swimmerboy2112]

Found a new winter project, goodbye kitty!

 

[rcrick]

With regard to the visual inspection in TN, it's a complete joke. The tech sticks a mirror under the car but I don't even think they know what they are looking for. I have an 08 civic that has the catalytic converter bolted directly to the cylinder head in the engine bay, there is not a cat anywhere underneath the car nor can the cat even be seen from under the car. Yet they still use the mirror and give me a visual pass every time. They could not possibly care any less about the job they are doing. If you pass the obd test and the gas cap pressure test, then you pass. Doesn't matter if you go in there and stink up the entire testing center with a hollowed out cat and 02 sim, you pass (or so Ive been told).

 

[Ryan_289]

Someone correct me if im wrong here.

Ive been told that on newer engines that were designed to be used with catalytic converters in the system, performance and mileage can actually suffer from complete removal. Something to do with losing too much back pressure. Not to say you need the super high doller oem cats, just some good quality aftermarkets.

Dont get me wrong, im not against you or anyone else taking them off. I probably would too if you could gaurantee me better performance and fuel economy. I think the old days of the super restrictive cats are long gone.

 

[SweetWaterSurprise]

With regard to the visual inspection in TN, it's a complete joke. The tech sticks a mirror under the car but I don't even think they know what they are looking for. I have an 08 civic that has the catalytic converter bolted directly to the cylinder head in the engine bay, there is not a cat anywhere underneath the car nor can the cat even be seen from under the car. Yet they still use the mirror and give me a visual pass every time. They could not possibly care any less about the job they are doing. If you pass the obd test and the gas cap pressure test, then you pass. Doesn't matter if you go in there and stink up the entire testing center with a hollowed out cat and 02 sim, you pass (or so Ive been told).

When I had my Civic the guy passed it over Camera they have in the ground for looking at cats. The guy proceeded to tell me I had no cat and I was going to fail. I had to force him to look under the hood to see where it actually was.

 

[Nelsonmd]

Someone correct me if im wrong here.

Ive been told that on newer engines that were designed to be used with catalytic converters in the system, performance and mileage can actually suffer from complete removal. Something to do with losing too much back pressure. Not to say you need the super high doller oem cats, just some good quality aftermarkets.

Dont get me wrong, im not against you or anyone else taking them off. I probably would too if you could gaurantee me better performance and fuel economy. I think the old days of the super restrictive cats are long gone.

I've heard the same. I'm talking out of my ass here, but it could have to do with the newer EGR and other emission systems that draw off the exhaust to go back into the intake, or something like that. Lower back pressure means disruption to the flow to the intake, something like that.

Also, removing the CAT on a new car will mean invalid readings from some of the sensors the engine uses for it's trim levels, so it could make the ECU run the engine at less than optimal settings.

 

[RyDog]

I had my 99 4runner for a while with no issues. Recently I drove down from the US to Belize. As soon as I ran through my first full tank of gas here I pulled a P0420. I have read that poor gas quality can contribute to the code popping. Would this mod take care of the CEL as well as the poor MPG that I am getting?

 

[alanflies]

An internal combustion engine needs a catalytic convertor like your butt hole needs a little plastic tube with a dryer sheet crammed in it...Sure it makes the exhaust a little less offensive to others and to the environment, but your butt hole doesn't really care at all...BBRRRRTTTT

It's only the exhaust sniffing fuel trim computers that worry over such nonsense...
Snif Snif...I think maybe you've eaten too much broccoli today...

Really though, I think the front sensor is responsible for tuning information, the rear one is solely to inform of catalytic convertor health...I.E. if the efficiency of the converter falls to below 95% efficiency, you get a code... simply letting you know your dryer sheet is losing it's ability to freshen up your flatus...so, the rear sensor mod= NO harm NO foul in my book.

 

[MattJakobs]

I'm trying to do this as I just had a P0420 pop up and I can't seem to find the rear O2 sensor. How far back is it located? I'm not sure if it differs year to year but I'm in an 01.

This is what I'm guessing to be the front..


And the rear?

 

[Doc2012]

[MENTION=109102]MattJakobs[/MENTION]:

It's right over the crossmember in the picture buddy......


You also have a Cali Emissions 4Runner, just FYI.

 

[MTD]

Haha, probably. URD has some big description of why only theirs works, but it's probably a load of crap =)

From the site:

Note: Be cautious of O2 sims that replace the rear O2 sensor with a falsely gererated signal.

Toyota started using a wideband type O2 sensor (air/fuel ratio) in the front position for better engine control. These wideband type sensors need to be recalibrated from time to time by the ECU. The ECU uses the rear sensors for this recalibration process. The ECU cannot properly recalibrate the wideband sensor using a falsely generated signal. This process is explained here, US Patent 5706654.

Use only a URD O2 Sensor Simulator on these vehicles to avoid poor performance, drivability issues and poor MPG.

URD in general is a huge crock of shit.... Their simulator is exactly the same as this, but is just $98 more. I am so tired of people praising their crap like it is the last word in tuning. Their statement doesn't even apply to your model year anyway (may want to check, could be wrong 99' was a funky year) since it has narrow band front and rear!

Edit: Just noticed this was a bumped thread, but my statement stands...

 

[Robb235]

URD in general is a huge crock of shit.... Their simulator is exactly the same as this, but is just $98 more. I am so tired of people praising their crap like it is the last word in tuning. Their statement doesn't even apply to your model year anyway (may want to check, could be wrong 99' was a funky year) since it has narrow band front and rear!

Edit: Just noticed this was a bumped thread, but my statement stands...

My '99 is Cali emissions and has a wideband front sensor.

 

[steve108]

There seems to be some confusion here. Only the front o2 sensor is used to adjust the fuel mixture. The rear o2 sensor is only used to monitor the performance of the cats. Removing or simulating the rear o2 sensor will not effect performance or emissions at all. Simulating the rear o2 sensor will let you remove the cats and not get a CEL. Only the California emissions 4Runners have two cats. Removing the cats on a stock engine will not gain much if any performance, but it's a way to save a bit of money if replacing the exhaust system, especially for those who live in states with no annual vehicle inspections. Outside of certain cities, I would have zero concern about any law enforcement even knowing what to look for as far as a catless vehicle is concerned.

 

[turbodudey2]

Question for OP

Before you get started, you'll need to run to RadioShack and pick up two items:

A 1 Microfarad (1μF) Capacitor - RadioShack part number 272-1055
A 1 Mega ohm (1MΩ) Resistor - RadioShack part number 271-1134

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)