colenzae

Got the P1135 code a while back & replaced the rear air/fuel sensor on the exhaust before the cat.
Cleared the codes out and after driving for a while got another cel.
Now its a P0136. Is this the O2 sensor after the cat???
Am I going to get another code for the third and final sensor after I replace this one??? ARRRRRGGGGHHHH!!!!
What has everyones experience been with these codes and sensors???

code58

Your front sensors (same R & L) are A/F ratio sensors. (B1S1 & B2S1)and your rear (after the cat is an O2 sensor-B1S2) My suggestion would be to clear the codes and see what comes back up if anything. It (P0136) may well come back up but that sensor doesn't go bad near as often as the front ones do. If it comes right back, it's probably time to replace it. The rear A/F sensor that you replaced is the 1 that commonly goes out 1st because it gets a lot more heat at the back of the engine. I wouldn't worry about the front until you have the P1155 come up. At least it's the easy 1 to change. If you're gonna worry about it, change it now and then you won't have to worry about it. It won't affect the operation much anyway if it is just the P1155. That's just the heater.

colenzae

BTW my rx is an 02' with 158,000 miles on it.
I find it interesting that many people recommend clearing the codes and then see if they come back. Or clearing them out and adding fuel system cleaner and running higher octane fuel.
I need to get this car inspected ASAP but she won't pass with a CEL.
I have disconnected the battery overnight and added some Lucas fuel system treatment and I'm going to fill up with super. I normally run standard 87 octane.
How long after clearing the codes should I wait to be sure all is well. 100 miles? 200 miles??

Lexmex

Today take that RX somewhere that you can get some quick takeoffs, taking you above 4,000 rpm and see if it comes back. I should mention that sometimes adding fuel system cleaner prior to a tailpipe test can lead to some issues on the readings (but normally I would recommend it, too). Usually, you should notice something with this particular code (if you did the quick takeoffs) after about 5 to 6 minutes. It's definitely focus on the sensor itself and not some connection or the vehicle ECM, that's what P0141 is for.

If it were me and it kept confounding me, I'd actually physically remove the sensor itself and take a look at anything out of the ordinary as sometimes some deposits or layering can build up on it.

colenzae

So I only got about 30 miles before the P0136 code came back. How hard is it to change the o2 sensor vs the rear bank air/fuel sensor I already changed??
I haven't looked at the o2 sensor mounting on my vehicle but I'm afraid the New York winters may have taken a toll on the mounting screws.
What I'm leaning toward doing is replacing not only the o2 sensor but the front bank air/fuel sensor as well and be done with it. I want to get 250k out of this vehicle so I figured replace them all.
The only thing is if after that I get a code for a bad cat I'll probably jump off a bridge!!

Lexmex

Let's hope not a P0420, that would be the cat code. The bolts are not that hard to remove, I recall they are like 14mm and definitely easier than that PITA a/f sensor in removing.

colenzae

Your lucky you live in a warm climate. Look at the mounting bolts on this sucker. It looks like the nuts are completely corroded away. I have no idea how I'm going to get this off. Any suggestions???

code58

It looks like the studs are stainless steel. Use an acetylene torch to heat what is left of the nuts and remove them with the needle nose vice-grips while they are red hot. (gotta work fast) Acetylene torch is called a hot wrench in cold (rust) country. IT DOES WORK! It will expand the nut and release the rust but you have to do it while the nut is still red. If you wait 15 seconds, the nut cools, shrinks and again locks on. You don't have to worry about getting the sensor out because the new sensor comes with a new plate to screw it into. A muffler shop might be able to help you out if you don't have an acetylene torch.

colenzae

Thanks for the reply. Sounds like a good game plan. I've been thinking of buying a small torch so now I have a reason to justify the purchase. I'll post my results.
Thanks!!

colenzae

Well all I had to do to get the sensor off was pull on the heat shield with a pair of pliers. With no screws left the only thing that was holding the entire assemble together was rust. Now I just have to clean up the threads and get new screws from Lexus.

code58

Good for you!