Rear O2 sensor bypass/CEL fix.

Awesome! Thanks for the clarification. Im gonna try and get it put in this weekend and see if it will fix my problem. any gain in fuel economy is just a bonus!

 

I'm gonna try and get the stuff for this soon. Truck has to get inspected.

 

I went by radioshack last night and picked mine up. They ad the drwaers marked by number and had both in stock. I was in and out in 5 minutes and it was 3.58 after tax lol. Had it together in 15 miunutes. if it works its the cheapest and easiet method I've seen

 

Yeah cheap and quick is what I like at times. I almost ordered it online because I didn't feel like driving to the mall. Just gives me a reason to go to bass pro and academy at the same time. I should have this done by next week and report back with results.

 

On lots of cars, this is the case, but on a lot of newer cars and other makes, the rears are a lot more involved. This is why IMO the URD sim is basically what the OP posted, a solid state circuit that alters the frequency and peaks of the oscillating narrow-band signal from a non-cat'ed sensor reading, down to what a cat'ed sensor output would be (slower, lower peaks). But it would be crucial to have data logs of a healthy OEM exhaust and sensor output, then a non-cat'ed output, and calculate the solid state's values. There is probably a green zone (great, totally tricks the ECU to the extent that its like the OE cat is there), and a yellow zone where the ECU still does not throw a CEL, but your air fuels are not optimal and a red zone, where a CEL gets thrown as the values are just too far off. IMO a sim that actually leans out the mix a tiny bit might be nice , as you don't need the OEM's tune of letting some gas get past combustion and into the exhaust to feed the cat, its not there.

 

Yah, If you folks hook this up and it works,,or doesn't,,or it goes monkey goofy on you,,report back either way. It was free to me, so I say share the find. Not going to crank these out for resale because it is so easy it's pathetic,,wouldn't make a dime due to shipping anyways. I am out of work and could use the cash,,but no. Free to me,,free to you.

Thanks for the sensor data info BSD,,good to know and more info to feed on for all.

HUGE DISCLAIMER!! if you guy's and gal's hook this up and it smokes spendy gear or causes irreversible damage to $$ parts,,don't even look this way. I don't see how it could and I looked at almost every avenue I could think of before snipping wires. Your on your own little campers.

 

OP, I test fitted mine tonight and ran it for about 20 mins with no lights or issues. Actually it's probably the best the truck has ever idled since I've owned it! I'm gonna solder it in and drive it for a few days and report back. Where did you mount yours at?

 

Cool,,Thanks.

Mounted it/secured it right by the sensor bung by the pipe using the wires I worked with as it's zip tie point. Folded it back against the wires and zip tied it down nice and snug.

One thing I forgot to add was that I used a double layer of heat shrink tube to insulate protect it. Slide one +/-3" section over the unit with some overhang,, shrink ONLY to what would be the top of the unit, then fold that unshrunk portion over to the side, and then slide your next layer over top of the fold and unit with again some slight overhang. Shrink it all down and trim off the top if needed. I loaded the open bottom with silicone by the attach legs and let it dry.

A person could also just use some thinned Tool/Plasti Dip (of which I had 2 cans but never made the connection). Dunk the whole thing minus the legs, let it hang dry, then attach.

It's not really needed,,but it's more of a rock/heat protection where mine is at.

 

Awesome! Thanks for the tip. My biggest concern was wether or not it would produce enough heat from electrical resistance to cause any issues so I had taken that in to consideration when I put it together. But after watching it run last night and periodically checking it for heat issues it doesnt seem to be a problem. I had thought about encasing it in some sort of clear resin or epoxy, and attaching a mounting tab, to protect it from water and mud, but I may go your route

 

Doesn't appear to be working for me. My OBD2 scanner is reading 0.0v for the rear O2 sensor. We'll see if the CEL pops back on though.

 

No CEL yet, but a weird observation. My AFR appears to have richened up by 0.5 to 1 point. Typically in closed loop it stays right around 14.7. This could be because I didn't reset the ECU when I did this mod.

 

Got a P0136 code. This mod doesn't work.

 

Have you looked at real time data to see what kind of reading you're getting from the O2?

 

Yep, 0.0v. I forget what it was before I did this mod, but it would bounce around between different values. Now it just stays at zero. Front O2 seems normal (mine is actually an AFR sensor up front, which is wideband).

 

Hmmm, perhaps that has something to do with it. Its been a while since my college auto classes, so I'm not 100%. Mine is a 96 which I dont believe has a wideband. I looked at mine with a MAC scantool, with my front O2 functioning properly and my rear showing 0.0v with this bypass installed. The only code I'm throwing is for the EGR (which is missing entirely). My fuel trims were within an exceptable range as well

 

To me, that indicates a problem. If the ECU is showing 0.0v, how can it possibly be happy with this mod and not throw a code?

 

By all acounts it should set a code but, for some reason on mine, it has yet to do so. As for yours this patent explains it in long and drawn out terms:
http://www.google.com/patents/US5706654?dq=Patent+number:+5706654

what it basically says in a nutsell is that on vehichles with a wideband sensor, they have to be calibrated with the ECU from time to time. To do this they use the downstream sensor, which in your case is a standard O2 sensor. This states that the ECU cannot recalibrate the wideband O2 sensor using a falsely generated signal (or no signal at all) which will trip the CEL. I think thats the case with yours, and that would explain why this works for some of us and not for others

 

OP,
out of curiosity have you looked at the voltage reading on your O2 sensor after this mod with a scantool?

 

My gas mileage went to crap after doing this. My AFRs are still about 1 point richer, so that's probably why. I guess those that have Toyota's wideband "Air/Fuel Ratio sensor" upstream can't do this mod.

 

No I did not, I don't own a scan tool. Never needed one.

Thanks for posting whatever results everyone gets from it. The upstream wideband stuff is interesting.

Still in the green with this Mod,,double checked the mileage on a refill the other day and I am up, right at 2 mpg. Not a huge gain,,but will take all I can get.