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Rear O2 sensor bypass/CEL fix.

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Old 08-02-2014, 09:20 AM   #41
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Quote:
Originally Posted by Yoda the Taco View Post
OP,
out of curiosity have you looked at the voltage reading on your O2 sensor after this mod with a scantool?
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.
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Old 08-02-2014, 04:01 PM   #42
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Quote:
Originally Posted by Yoda the Taco View Post
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/US5706...umber:+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
I tried reading the patent information, but it was so dry and boring I kept having to re-read what I just read. After about 6 paragraphs of that, I had had enough. Can you cut and paste the section where it talks about calibrating the upstream wideband off of the downstream narrowband?
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Old 08-03-2014, 01:20 PM   #43
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Rear O2 sensor bypass/CEL fix.

Reversed the mod and heat shrinked the rear O2 wires back to stock. Rear O2 activity returned to normal, and AFRs returned to 14.7:1.



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Old 08-03-2014, 01:25 PM   #44
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Quote:
Originally Posted by Robb235 View Post
Reversed the mod and heat shrinked the rear O2 wires back to stock. Rear O2 activity returned to normal, and AFRs returned to 14.7:1.



What app did you use? How did you get the trans temp?
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Old 08-03-2014, 06:49 PM   #45
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Originally Posted by ARB1977 View Post
What app did you use? How did you get the trans temp?
Engine Link app on my iPhone. Check out my write up here:
http://www.toyota-4runner.org/3rd-ge...ur-iphone.html
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Old 08-03-2014, 07:03 PM   #46
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Rear O2 sensor bypass/CEL fix.

Ok, I think I figured it out. If your OBD2 scanner is reporting 0.0v for the rear O2 sensor, then you've done the mod incorrectly.

I think the original instructions in this thread are kind of vague and sort of misleading. The way I interpreted the instructions are drawn out in my first diagram labeled "incorrect". After Googling, I realized that I had wired this thing up wrong. The second diagram, labeled "correct" is how it should be done.

I'm now getting a voltage signal from the rear O2 sensor again. It seems to hang around 0.5 to 0.4 volts typically, whereas before the mod, the values would bounce around quite a bit. I'll drive this around for a while and report back on whether I get a CEL or not.

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Old 08-03-2014, 09:34 PM   #47
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Here ya go,,this was one part that I had found after much searching. Tell me what you make of that,,anyone chime in.

http://www.vfaq.com/mods/O2bypass.html
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Old 08-03-2014, 09:56 PM   #48
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Originally Posted by Robb235 View Post
Engine Link app on my iPhone. Check out my write up here:
http://www.toyota-4runner.org/3rd-ge...ur-iphone.html
My phone is a android but does the torque pro app monitor trans temp on 1st gen Tacomas?
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Old 08-04-2014, 02:37 AM   #49
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Originally Posted by ARB1977 View Post
My phone is a android but does the torque pro app monitor trans temp on 1st gen Tacomas?
Yeah, it does. I've not used it myself, but there's a long thread about Torque on here somewhere. As long as your truck is '99 or newer, you can monitor transmission temps.
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Old 08-04-2014, 03:09 AM   #50
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Rear O2 sensor bypass/CEL fix.

Quote:
Originally Posted by Mod View Post
Here ya go,,this was one part that I had found after much searching. Tell me what you make of that,,anyone chime in.

http://www.vfaq.com/mods/O2bypass.html
I'm pretty sure the ECU needs to see some kind of voltage reading from the rear O2 sensor. In fact, I believe this is why URD's O2 sim has to plug into a working rear O2: it has to have a signal from the sensor that it can modify and send to the ECU. For those that have eliminated the O2 sensor from the circuit, and are just using the resistor and capacitor, I have no idea why some people aren't tripping the CEL. I wonder if the ECU's catalyst test is placed in a constant state of "Not Ready".
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Old 08-05-2014, 01:36 AM   #51
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the only thing is your truck uses the o2 sensors to adjust fuel trims...Air Fuel Ratio..
tricking it seems like you will be running rich or lean like always I wouldnt suggest doing this.but thats just me....
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Old 08-05-2014, 02:42 AM   #52
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Originally Posted by lunch box View Post
the only thing is your truck uses the o2 sensors to adjust fuel trims...Air Fuel Ratio..
tricking it seems like you will be running rich or lean like always I wouldnt suggest doing this.but thats just me....
We are talking about the rear O2 sensor, not the front. Yes, tricking the front O2 sensor would be a bad idea.
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Old 08-05-2014, 05:19 PM   #53
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Rear O2 sensor bypass/CEL fix.

Well, it's been 2 days and the CEL has stayed off. Granted my only driving has been short drives to work and home, however this is the longest the P0420 code has been gone. When resetting the CEL in the past, the P0420 would come back pretty quick. I'll take a long drive here in the next few days and see if the CEL comes on.
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Old 08-12-2014, 07:25 PM   #54
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CEL has continued to stay off. This is by far the longest I've gone without a P0420.
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