Rear O2 sensor bypass/CEL fix.

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?

 

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?

 

Engine Link app on my iPhone. Check out my write up here:

 

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.

 

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

 

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.

 

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".

 

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.

 

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.

 

CEL has continued to stay off. This is by far the longest I've gone without a P0420.

 

CEL still off. Disconnected again the other day, to make sure the CEL was working,,and it was. Reconnect of resistors and reset of the brain box turned it back off.

 

Sub. This is a great find. For the last year and a half I finally found an answer. I took off my first cat and only running the 2nd one because I added the LCE long tube headers. I've been running with the CEL on this entire time. Time to give this a shot before I dish out the 120 for the URD part. Thanks for the write up and info. I'll do it tomorrow and give you guys an update.

On my engine link it isn't reading Heated Catalyst.It.s not reading BK 1 Sensor 1 O2 Voltage. But I am throwing the code P0420

 

Yup, anyone who tries this please report back for all to read. Thanks.

 

So since I'm a double cab my connection was under the front passenger seat.
I removed the seat lifted up the carpet and there it was. This is how i set it up. I also disconnected the battery before anything was done. I'll update this post in a day or two. Runs for a while. Fingers crossed.

 

Update.... So I ran this mod for a day and my O2 was reading 0. So I switched it to the way the 4runner has it done and now i'm reading the O2 is reading 45 or so. On both mods the check engine light was off. Right now the way I running lean. 14.28 I also had the truck put on a dyno to really check the reading form something other then my app. So my question is is 14.28 to lean?

 

Is 14.28 in open loop or closed? Typically the ECU keeps AFR at 14.7 in closed loop, so it sounds like you're running a tad rich, not lean if you're at 14.3.

 

My truck was also a cali truck like your runner. So I think it's an open like yours.