dragr1

iTrader: (3)

My 1999 4Runner popped up a check engine light, so I went to Autozone and it read P0136 Bank 1 Sensor 2 Sensor Circuit Malfunction. I did a search and confirmed it is the O2 sensor-but is it the one between the motor and cat. converter or the one after the cat. converter?

Maybe this has something to do with my crappy gas mileage even though it runs fine?

paranoidandroid

most likely the 02 sensor before the cat. that one always goes bad first.

bamachem

i had a sensor 1 light a while back. unplugged it, disconnected the batt, reconnected everything and haven't had a problem since...

give that a try, and if it doesn't work, then get an O2 from gadget.

wrenchmonster

Hummm. Be careful here. The left bank (bank 1) is the driver's side, the right side (bank 2) is the passenger side. (At least for GM, I fairly certain this holds true for all vehicles). The O2 sensor closest to the engine will be sensor 1. The one on the same side further down stream will be sensor 2 (post cat).

A false code for sensor 2 can occur if sensor 1 is bad. Basically, sensor 1 sees what happens before the cat. Sensor 1 will toggle from roughly 100-800 hz. Sensor 2 will toggle far less, say roughly 100-300 hz. This tells the ECM that the cat is doing it's job. If the cat were bad, similar readings would occur between both sensors. This causes the ECM to throw a P0420 code, poor catalyst efficiency. However, if your first O2 sensor is bad, then the second O2 sensor will read differently and will throw a code for a bad O2 sensor. In short, you need to check the O2 sensor upstream, and the cat. Once you know these are bad, then you can work on condemning the second O2 sensor.

-Wrench

dragr1

iTrader: (3)

I'll try that, I think I have at least one O2 sensor fom a previous parts trade anyway.

dragr1

iTrader: (3)

Ok, I fixed this a while back by ordering an O2 sensor from Gadget. But, over the weekend the same code has reappeared. Did I get a bad 02 sensor or is my ride just smoking crack?

I had Autozone erase the code, so we'll see if it comes back.

bamachem

hmmmm.

you did replace sensor 2, the one behind the cat, didn't you?

you may want to pull it and take a look. make sure it's not very "sooty" and make sure the plug is secure and fairly dry. did you use electrical contact grease on the plug? if you did, make sure you didn't get too much on there so that it's shorting out in some way.

MTL_4runner

Like Andy said, Bank 1, Sensor 2 is after the cat (there is only 1 bank of sensors on a 3.4L).
That one rarely goes bad so I would try to get down to the root of what's causing them to go bad.

This thread might help too (notice also may be a leak at the cat):
https://www.yotatech.com/forums/show...ighlight=P0136

dragr1

iTrader: (3)

Huh, that has some promise b/c I have been hearing what I think is a small exhaust leak, but I though it was more toward the manifold. I'll have to check it out.

Yes, I did replace the correct sensor.

Fink

I am having this code now after installing the Rear 02 Sensor Simultator from Gadget and was wondering if you ever got this resolved and what it ended up being.

Before this I was getting: P0420 Catalyst System Efficiency Below Threshold (Bank 1)

So I got a hold of the URD simulator...and now this code has been thrown.

If anybody knows what might be going on that'd be great!

Thanks,

Fink

MTL_4runner

Fink, did you get the O2 simulator so you didn't have to fix the P0420 code?
Am I missing something here?

Fink

Right. The simulator is installed, and I am now getting this new P0136 code and NOT the code I was getting before the sim was installed.

My other thread https://www.yotatech.com/forums/show...t=67521&page=3 has more info in it about the problems I have been having with the simulator.

Fink

Mr. Bob

the downstream 02 is there to watch what the cat is doing... this was to comply with OBDII... your downstream sensor may be working just fine, but seeing the catalyst be less efficient ... this could be a bad cat, or it could also be a pre cat problem... IE extra emmisions the cat cant take care of...

Testing is the best way to go... get on the upstream 02 and watch what it is doing... then go to the downstream and watch it... the only tool that will work properly is any form of graphing multimeter... if you dont have the ability to test these components properly, find sombody who can... even if it costs you a few $$ it could work out cheaper in the end than throwing parts at things...

and bank 1 will always be the bank with cylinder 1... GM that is the drivers side, while Ford is the pass side...

Hope this helps you

Bob

dragr1

iTrader: (3)

The code hasn't reappeared since I had Autozone erase it, and I just put over 750 miles on it over the holidays.

Fink

Regardless of the O2 sensor's performance, the simulator is supposed to fake out the ECU and make it think that everything is within spec, it's obviously not doing that. I had my dealer clear the code and we'll see if it throws it again...if not, I'd be the happiest man alive. I was hoping after this week the Runner would be set so hopefully I can get all this figured out before my classes start kicking it in gear and I'll be tied up for the rest of the semester with that.

Thanks for all the help and I'm really sorry for taking over this thread, if the mods would like me to make another thread or put this in my thread I'd be happy to.

Thanks guys!

Fink

Mr. Bob

Hey Fink... This is simply a thought... what is the downstream specs for a non california emisions runner?? are they the same as the california emissions?? what if you are feeding the ECU the wrong voltage?? that would set that light right off..... is that simulator designed for your application ( california )?? or is it for the rest with a single cat?? maybe they are all the same?? but its a thought.... what voltage is the simulator feeding the ECU? do you know???

Cheers
Bob

Fink

No idea man, I could check.

I think the first step is to hear back from Gadget about it and then go from there...hoping to have that done by tomorrow morning/early afternoon.

After that I will be stuck here all afternoon so we can throw around some ideas then and go from there.

I'm really hoping I didn't just cut up my ECU wires for nothin!

Fink

dragr1

iTrader: (3)

Would you guys believe that this dang code has appeared again! Just had Autozon turn off the code today, so we'll see if it comes back.


Could this be associated with anything else-like an exhaust leak or something?

Does this sensor actually do anything other than emissions anyway-I mean isn't the front sensor actually telling the ecu how much fuel to squirt?

kevin444

Im having the same problem as fink, i got the p0136. Running the 02 simulator from urd, my connections are clean well twisted and soldered and heat shrinked The only i can think of im running a test pipe and the gaskets are not sealing up or the gasket for the 02 sensor thats on the test pipe. I do not notice any performance changes just annoyance.

From autozone code reader: 2 errors present


p0136 02 sensor malfunction bank 1 sensor 2

p0136 o2 sensor circuit malfunction bank 1 sensor 2

blackdog76

I know this is an old thread but I just installed the URD sim and the same thing happened. The sensor is a plug in and play deal now, no wiring. Was getting the 0420 code before and now the 0420 and 0136. What's the fix?