anyone have the schematic or know the wiring for 2005+ Tacoma rear O2 sensor? figured i'd ask before i go tapping into the wires.

 

Don't know the wiring, but why are you tapping into the rear O2?

 

i am installing a wideband O2 which will be used to feed accurate AFR readings to a seperate fuel and timing unit. however, i wish to keep the OEM ECU and i do not want/need the OEM O2 sensor in my exhaust. i'll make my own O2 simulator to keep the ECU happy.

 

I don't believe you get accurate AF ratio readings after the cat has cleaned it

I have some diagrams. What engine you have?

 

how do you mean "after the cat has cleaned it"? my wideband O2 wont be behind the cat.

my engine is 2TR-FE

 

in that case, you'd be looking for the front O2, as the rear O2 is behind the first cat. (just confirmed this by looking at mine)

 

...yes, you are correct. i still dont need the rear O2 in the exhaust.

 

Yes, you do. If you don't, the ECU will throw a code and you won't be able to pass emissions.

 

in his defense, he did say he would make an 02 simulator to keep the ECU happy for the sensor he didn't need. But, if your going to make a simulator, and keep the engine thinking its reading its own exhasut and appropiate 02 levels, why not just let it actually read its own 02 levels?

 

plus, with the second O2 sensor still installed, it'll still let you know if your cat is crapping out.

 

Right... And the simulator is usually used in the front sensor so that you have control over faking the ECU into open loop for tuning.

The rear O2 sensor is there to keep an eye on the cat (like DZ pointed out). It's a small function, but it's "required by law". As such, the ECU will throw a code if it doesn't see it there, or if it's malfunctioning. And, as such, you'll fail emissions since your check engine light is on.



ahhh... wait a minute. I screwed up.

So, are you looking to run a MegaSquirt II or somesuch and completely do away with the stock ECU?

 

oem ecu will stay. i've decided to go with a piggyback unit, so the front O2 will stay and i will install a wideband O2 for monitoring the AFR more accurately. i still want to run a sim on the rear O2.

so far, its just been a few replies as to what the O2's do. i know that already, was looking for the wiring diagram. i'll probably just buy the service manual and run some voltage tests on the leads so i can build a small sim (voltage regulator and heater load).

 

with a sim i dont need the O2 sensor in the exhaust, thats what a sim does.

 

i dont need the O2 to tell me this. my emmissions will meet or exceed CA emissions standards, even after i install my turbo.

 

Google...

http://www.google.com/search?hl=en&l...am&btnG=Search

http://www.ecanfix.com/~mdhamilton/o2sensor.html


I don't want to beat a dead horse here, but are you thinking that an O2 simulator is just about maintaining a constant voltage? It's not, and the ECU will recognize a constant CV as trouble and throw a code.

This is the reason I'm kinda' busting on you. I had a feeling that you may not quite be sure about how a sensor works and what the ECU expects to see.

Many of the simulators are more correctly described as "conditioners". Down that line, these can help:
http://o2simulator.com/
http://splitsec.com/products/conditioner.htm

The reason to run a conditioner is so that you can make the emissions folks happy in terms of the OBD II interface being happy. The ECU will still see the stock O2 sensor in the loop, but it'll get out of the way when you want it to.


Now, if you're really looking for a true replacement, you'll have to do a bit more circuit work. Check here:

http://www.bobblick.com/techref/proj.../o2sensor.html

The final circuit he describes is here:
http://www.bobblick.com/techref/proj...sim/o2sim.html


Whichever route you chose, you will have to BE SURE that the ECU thinks that there's a sensor out there. If there's not, it'll set a flag (but maybe not throw a code) and when you head for emissions testing, and they plug into the ODB II side of the ECU, OBD II will report the issue and they'll fail you.


At the end of all this, I guess I'm still curious as to why you don't just stuff the rear sensor in the pipe, let the ECU see it and be done. You're running a stock ECU, the rear sensor isn't affecting performance, and having it there will save you a ton of time in building and debugging a real simulator.

None the less, you have the info to take whichever route you choose.

 

i dont want to argue my case, but the links you quoted are not specific to a 2006 Tacoma, and the other link to making a O2 Sim circuit is for adjusting the AFR (sim for front O2). i'm only sim'ing the rear O2.

as for why i dont want the rear O2, is because the cat might not be there while i run turbo on a daily basis.

 

All O2 sensors work the same (in the scope of what we're talking about), and faking out either O2 sensor needs to be done the same way. The ECU expects to see the same types of signals from either one.

The bottom line is that you can't just toss a 0.8v regulated voltage in there and expect it to work.

I'm trying to help... But feel free to ignore it and do what you think is best.