Robb235

This is wrong. URD's O2 simulator piggybacks off the rear O2 sensor, it does not generate it's own signal by itself. If you actually read URD's description, you would see that some Toyota vehicles (including mine) use a wideband up front that periodically is calibrated off the rear O2 sensor. If URD's O2 simulator was truly making it's own signal "from scratch" as you say it does, then it wouldn't work correctly.

DailyDrive

How does the rear O2 sensor generate a signal if there is no cat?

Robb235

Is this a serious question? It generates a signal the same way your front O2 generates a signal (assuming narrowband up front). It will generate a different signal if you have a cat versus not having a cat, but still generates a signal. Do you think that the rear O2 sensor goes completely dead or something if the cat is no longer present?

kcebes

Glad to hear it! I'll be doing this to my 2001 tomorrow.

DailyDrive

Yes, O2 levels without a cat present will be way too high, outside the sensor's design range. So the sensor will basically output a flatline voltage.

That's why for people who have a catalytic converter on the way out, the resistor method works. It shifts the voltage coming out of the sensor using a rather perverse version of a voltage divider. But once O2 levels are too high, the sensor won't be able to generate the required sine wave, as both the high and low levels of O2 will be above the measuting range of the sensor.

And that's why people that have gutted cats don't bother with resistors. They need a simulator.

Robb235

Wow... I'm not sure whether to take this conversation with you any further or not. You clearly have no idea what you're even talking about, which has been apparent throughout this entire thread.

First off, if the cat is working, the rear O2 should be steady, compared to the front O2 which will be oscillating between rich and lean (again, assuming O2 upstream, not the wide range air-fuel sensors). If the rear O2 is oscillating similar to the front O2, then the cat would certainly be suspect.

The rear O2 sensor will not "flatline" in the presence of a missing (or faulty) cat. It'll do the opposite, it'll mimic the wave form of the front O2. If the cat is working, you'll see the rear O2 settle into a steady voltage while cruising.

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DailyDrive

You have pretty much everything backwards.

If you don't trust about 1000 articles online about what the rear O2 signal should look like, here is a quote right from the Toyota service manual:

"If the catalyst is functioning normally, the waveform of the heated oxygen sensor located behind the catalyst switches back and forth between rich and lean much more slowly".


You say: if the cat is working, the rear O2 should be steady

Toyota says: the waveform of the heated oxygen sensor located behind the catalyst switches back and forth

Robb235

You either don't understand what you're reading, or you're intentionally choosing to take the FSM out of context. You even posted it yourself... "...back and forth between rich and lean much more slowly". There you have it. In the presence of a properly functioning cat, the rear O2 reported voltage will be much more steady when compared to the upstream O2. Sure, some switching will occur, especially under varying engine loads and such, but it should be far less frequent than what you would see from the front O2. If the cat has failed (or is removed), then the rear O2 sensor is seeing the same untreated exhaust as the front O2, and you will see the two waveforms mimic each other.

I'll even post some 3rd party info for you:

Robb235

And another thing, in a previous post, you claimed to build a copy of URD's simulator...


Prove it. Prove that you actually built it, because I'm calling BS on this. In earlier posts, you incorrectly described how URD's simulator worked, saying that it generated it's own signal entirely, instead of piggybacking off the rear O2. This demonstrates a complete lack of understanding on your part, and gives me zero confidence that you actually built this like you say you did. Provide pictures, wiring diagrams, specs of the parts used, something that proves you actually did build a copy of URD's O2 simulator. Because based on your previous posts, I'm pretty certain you didn't.

DailyDrive

So which one is it? Is it steady or switching? Both of those sentences came from you, and they contradict each other.

You were correct on the 2nd try though. The switching is absolutely mandatory. A proper O2 output will switch from between 0.1v and 0.9v around once every 3 seconds. If it's doesn't switch, or switches too fast, or switches too slow, it will throw a CEL.

This quote is correct, except you are interpriting it incorrectly.

The key word there is "average reading", not "levels off". Can you tell me what the average voltage reading of a sine wave that cycles between 0.1v and 0.9v? I'll give you a hint, it's right around 0.45v.

Again, the cyling is mandatory. If your rear O2 sensor outputs a steady signal of any voltage, it will throw a CEL.

I should say that I have no relationship with URD and never owned or disassembled their product. But the last time I looked at them, which was more than 5 years ago, they sold an "O2 simulator". They key word there is simulator. They advertised the product as a guaranteed method to get rid of P0420. That code can be thrown for many reasons, it could be a dead O2 sensor, a fouled up O2 sensor, a dead cat converter. The only way to fix all those problems is to completely simulate the rear O2 signal, which I assumed it did.

I also looked at various other aftermarket solutions, and they all worked on the same principle, by simulating a switching/cycling signal that would be sent to the ECU in a properly working system.

If the "new" URD "simulator" really does "condition" the signal from the rear O2 sensor, and depends on it to be there, and working, then it's a terrible solution, just like the resistor method.

For the reasons:

1.) A rear O2 sensor has a finite lifetime, it will become non-functional with age, and will not generate a switching signal. If the URD relies on the signal from the rear O2, then if your sensor goes out, you will end up with a CEL.

2.) The same for catalytic converter, it will degrade with age to the point that even a working O2 sensor won't output a signal, you will end up with a CEL.

3.) A rear O2 sensor's heater circuit has a finite lifetime, it will become non-functional with age, you will end up with a CEL. Just a different code, still a CEL.

A real O2 simulator is a very simple circuit. I've built one in a few hours with $1 of parts, and it has been working flawlessly for years.

Here is what it looks like:





It's incredibly simple, outputting a square wave signal that switches between 0.1v and 0.9 with a period of around 3 seconds. I will never have to replace my rear O2 sensor or the cat converters as it doesn't depend on them in any way anymore.

vasinvictor

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I need to do the resistor hack too. That's the only code I throw (although I put a high flow cat back in) and I get tired of the orange light glaring at me. I think I'll go get the materials tonight.

edit: I dind't read to the end of the convo. I have a wideband installed after my turbo. When I was catless that wideband would sweep quickly from 13.9 to 15.4. After the high flow cat, the wideband slowly sweeps from 14.6-14.8 while cruising and doesn't bounce around nearly as much. Guess that $40 Ebay cat works! But then a $40 Ebay cat is just a hack for not having a real Toyota brand cat, and my turbo is just a hack for having too small of displacement. And my 4runner is just a hack for not having a time machine, etc etc etc.

Robb235

Wrong, my statements are in agreement with each other. Which I noticed you left out a part of my second quote in order to make it seem like I was saying something that I wasn't. Cute.


Statement 1: First off, if the cat is working, the rear O2 should be steady, compared to the front O2 which will be oscillating between rich and lean.


Statement 2: In the presence of a properly functioning cat, the rear O2 reported voltage will be much more steady when compared to the upstream O2. Sure, some switching will occur, especially under varying engine loads and such, but it should be far less frequent than what you would see from the front O2.


You conveniently left out the part in red. My assertion still stands that the rear O2 sensor will be steady when compared to the front O2 sensor. You need to comprehend the italized part. Yes, some fluxuations will occur. But on a properly working rear O2 with a properly working cat, downstream O2 will not be constantly jumping from 0.9 to 0.1 like the front O2 does. This has been documented over and over and over again, yet you state the opposite.



Wrong. Once again.... a rear O2 should not be switching from 0.1v - 0.9v every 3 seconds if the sensor and cat are both working properly. That sounds more like the behavior of a properly working upstream O2.


I can't seem to get this through your head, so maybe Eric The Car Guy can:

Robb235

Now to respond to the second part of your post:


Wrong. The "levels off" aspect is an important aspect to take note of. Can I tell you the average reading of a sine wave between 0.1v and 0.9v? Sure. It's 0.5v. Can I tell you something else about that sine wave? It isn't leveled off.

So URD's O2 sim is a terrible product? LOL! You heard it here first, folks! Despite all the positive feedback in the various Toyota forums, URD is selling you a "terrible" product!


Good thing you don't have a California Emissions vehicle.

DailyDrive

You are just digging your hole of ignorance deeper and deeper.

Here is a company that sells real O2 simulators. Watch the video they have, it explains how it works. Notice the blinking light, they'll tell you what it means, if you can't figure it out. Get your stop watch out and count how often the switching happens (light blinks).

It basically supports everything I said, and disproves everything you keep saying.

http://www.ubertechnics.com/O2_Simulator_2.5.aspx

[YOUTUBE]0kptjLUyq_c[/YOUTUBE]

Robb235

LOL! That proves absolutely nothing. Just because the box he built satisfies the ECU (he claims), that doesn't mean that the output of the box is what an actual downstream O2 sensor is reporting in the real world. Again, please watch the YouTube video I posted for proof of this.

Just out of curiosity, do you still stand by your assertion that the rear O2 "flatlines" when the cat is removed? I mean, after all, you did ask me how a rear O2 sensor generates a signal if there is no cat (LOL!). Do you still stand by this statement?

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DailyDrive

Ok, so that company that sells that O2 simulator according to you is making "claims".

Here is another company that sells a similar product, look at the manual for the product.

http://www.symtechlabs.com/support/d...imInstall3.pdf

And again, it visually shows how the signal should look. Yup, it cycles. How surprising!

Robb235

And once again, my point has apparently gone completely over your head (or you've chosen to ignore it). Let's try this again...

Just because that O2 simulator's output satisfies the ECM, it does NOT mean that is what a real life, working downstream O2 sensor's output looks like. Did you even watch the Eric The Car Guy video? Look at what a properly functioning rear O2 looks like; it behaves in the manner that I have described to you multiple times now, and not in the manner you have described.

Sent from my iPhone using YotaTech

Robb235

Also, you didn't answer my direct question to you from earlier. Do you still stand by your quote below? Do you still assert that a downstream O2 will "flatline"?
Do you still stand by this statement?

DailyDrive

You keep changing the subject, but I'll give you an answer and an explanation! Maybe you'll even learn something!

Yes, in theory an O2 sensor with a removed or high flow or just old catalytic converter will "flatline" in the 0.9v range. This happens because the oxygen content in the exhaust gases exceeds what the O2 sensor can measure.

Have you heard of another hack solution to the P0420 problem involving spark plug non-foulers and various spacers?

http://hydrogengarage.com/o2spacer.html

Do you understand now? The spacer basically lowers the level of oxygen the sensor sees, so the varying levels of O2 in the exhaust gases come back down to the O2 sensor's measuring range, and it can again generate a sine wave, that crosses the very important 0.45v level, that the ECU is explicitly looking for.

If there is no switching signal coming from the O2, you'll get P0420. If it doesn't switch between 0.1v and 0.9v while crossing 0.45v, you'll get P0420. You keep denying this basic fact.

JasonYota

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