Rear O2 sensor bypass/CEL fix.

Huh?

Both Federal emissions and Cali emissions trucks will switch between open and closed loop. Closed loop for typical cruising around, open loop when you hammer the throttle. Typically in closed loop the AFR right around 14.7. Open loop it gets much richer.

 

Ok then.... maybe I'm going to have to do more research. thanks bud

 

Running a 14.3:1 A/F? Sounds like the resistor/cap values need some tweaking, as my fears in post 18 are valid, the rear narrowband o2 is used to calibrate the front wideband sensor (01 for trucks, 99 or something for 4runners).

For the torque app question, my torque app shows my 01's trans temp. I have the paid app that has more PIDs loaded. For the free app, you need to go in and make the PID settings.

 

^^^ well on the other hand you guys have a working a/f sensor. I just finished testing mine and at cold temps its at 1.0 and on heated temps it's at 1.2-1.3 so it's not working. Im going to order one hopefully friday if funds are there. But as for it removing the CEL it did do that.

 

i found this thread and did this mod a few weeks ago. it worked for me BUT, i took my exhaust off the other day and removed the insides from the cats. truck threw a code just now while dropping my daughter off at school. not sure what code yet due to my bluetooth adapter being left in the girlfriends car. i'll have it back tonight and check sensor voltages and what code threw off the cel

anyone had issues with this mod not working with out cats?

2002 3.4L double cab 2wd TRD

 

sensor voltage is good at .5v and stays pretty steady. code is for the rear O2 sensor. P0136. I started researching it and i'm guessing there is too much exhaust flowing passed the sensor. so instead of trying to space the sensor out of the pipe, i bought some stainless steel zip ties and i'll try to wrap the sensor to cut the flow down. see how that works out.

 

Thanks for the update. Still trucking along without codes or issues. Hope your ss zip tie trick works.

 

well i haven't had any time to pull the O2 sensor yet, but i reset the code and have drove about 60 miles since then and it has stayed off. i'll update if that changes. thanks for the knowledge by the way.

 

Can't take any credit for this mod,,but thanks. This was figured out by someone else back in 2002 I think,,I just passed the info along to maybe help other folks.

 

I'm curious, did you ever do anything to reduce the flow by the sensor? Or has your CEL not come back?

I've got a '00 3.4L Taco. Originally, I had P0136 and P0420. So I soldered in the cap and resistor as shown and reset the codes with my basic scan tool. After - no CEL. But then, after a few days of normal driving, my p0136 has come back. Still no P0420 though. Is it possible that I just need a new downstream O2 sensor and this mod won't work unless the sensor is working?

Thanks in advance for any help.

 

i never got around to doing the zip tie thing. my CEL pops up with the p0136 every few weeks. i just reset it. although, i recently finished one project and am thinking of going back and "wrapping" the O2 sensor and see if that changes anything.

 

Take it for a drive after you are done, then go home and pull the battery cables,,overnight. I did two of these setups on other trucks (same gen), one never came back on, and one popped on after a few miles. Had him take it home a pull the battery cables for 12-24 hrs and try it again. He said it was about 18hrs then the batt was plugged on and he drove off. Has not shown since. About 5-6 months on both so far. One was a 99 SR5 2.7 4x4, and the other was a 2000 same deal.

If you guys are soldering, make sure you have a heat sink clipped between resistor and hot work. You can overcook those criticals and change the value of those, or you will kill them altogether. A simple set of hemostats that jaw lock, clipped between resistor and hot work, or a tight fitting alligator clip will draw heat off long enough. Silver bearing solder is what you want to use.

 

Has anyone heard pro's & Cons on taking the Cat converter off of a 3.4 v6?

I had a upstream 02 sensor go bad because the previous owner put a universal sensor in, so I replaced it.
While replacing it I finally realized that the PO took out the cat converter and just straight piped it to the muffler
Now I am throwing a P0420 code.
I would imagine with the muffler would have enough back pressure, just not sure.

Since I have changed the 02 sensor the truck will surge while stopped.

It is throwing Bank 1 knock sensor code after I just had them replaced. I am still underway on trying to fix that.
Just trying to get any insight on the Cat that may be causing additional issues.

Thanks again

 

Knock sensor code could be a connection prob since someone else did it?. Finding a good mech that will treat it as his own is becoming significantly harder. Always DIY if you can, and I already know that some don't have that access due to whatever. If you did it all yourself,,your ahead of the game and congrats.

You replaced the knock sensors due to a code issue beforehand?,,or just maintenance?. This could be causing your surge at idle.

The pros and cons kinda cancel each other out, due to being fuel injected and computer control.

With that being said, I am without cat on my 2.7 since about, eh, 2004. At that time with less overall mileage, I felt a improvement in hill climbing and that's about where it ended and to be expected. At that point in time, the CEL light clicked on, stayed on, and was just recently extinguished by this thread findings and making the connections. I could also put out the light if I held high rpms when climbing the hills loaded, heating the sensor enough, cleaning the burn, to kill the light. Once hill crested and cooling down,,the CEL would pop back on. That told me what I needed to know. The gas mileage and unloaded and loaded hill power stayed about the same.

Is it going to be the same with your V6?? Not all trucks and engines are created on the same work shift unfortunately.

If your throwing a PO420 code, you can try this diode trick, as you are sitting about where I was after the straight pipe went in.

 

If you're getting knock sensor codes, look at replacing the wiring. A lot of times they go bad on these motors, which causes the ECU to think there's a problem with the sensor itself.

Are you supercharged?

 

Not supercharged.

I replaced the wiring harness on the knock sensors as well. (from Toyota)
I unfortunately replaced the knock sensors with aftermarket ones off of Rock auto.

They were throwing both knock sensor codes and after a couple of diagnostics. I had a mechanic change them.

It ran good for about a day and its just been hit or miss since then.

It started throwing the upstream o2 sensor so i changed that and now it is giving me the p0420 code and only one of the knock sensor, bank 1 sensor codes.

I see in previous threads that you can by pass the downstream sensor. Would not having a cat throw a P0420 code?

Im thinking the knock senor is either a short, bad computer or possibly shitty knock sensor's.

Im kinda lost on the P0420 code


thanks

 

It sounds like the aftermarket bit down. Grab some OEM knock sensors and have those put in or put them in yourself. Absolutely oem on a knock sensor. That one is a fuel and timing master signal and should be top shelf quality and be treated as such.

Yes. Not enough back pressure and heat held on the sensor. It's not getting a good whiff or none at all of the gases racing by. You could have both o2 sensors oem new, no cat but the test pipe in place, and you could still throw a PO420.

 

So quick question for you guys since everyone seems to be going back and forth whether this is working for them or not. I have a v6 double cab that has no muffler and a gutted 2nd cat. My truck has been throwing a p0136 code for a long time now. Every time I reset it it pops back on the same day. Would this mod fix it? From what I understand, the p0136 is most likely from a bad sensor. I replaced an exhaust gasket a while back, then got a p0140 code for a little bit, reset it, then got the p0136 again. I'm assuming if I buy a new downstream sensor it's gonna throw a p0140 code again telling me I have a bad cat. Just wanted to know what you guys thought of this it has stumped me for the longest time and ready to turn that light off

 

Only way to know if it will kill the light,, is to try.

With your deal of no muffler, gutted cat, and V6, it's a crap shoot for me to say yes or no that it will work. I still have a OEM muffler in place and a I4.

Your new exhaust gasket install probably flustered the computer for a cycle, then it went back to it's old code after it was reset. So that could in theory tell you that the sensors are working and reading. The flip side is that some part of wiring harness(s) might have been stressed during the work and it threw gonzo codes afterwards.

You could test both sensors and verify that they are still in good shape, then proceed with the mod.

 

Okay thanks yeah I'm going to go pick up the stuff for it tomorrow. I appreciate you still responding to this thread even though it's a couple years old lol. This may sound stupid but how exactly could I test the voltage? I don't think I can do it with my scanguage 2. I do have a meter that can measure voltage and ohms and all that good stuff should I just stick the leads into the wires or what?