wvuguy

My 99 RX300 with 142k mile is throwing codes p0171,p0125 and p1155. After doing some research I believe I need the front A/F in between the motor and radiator. I see two Denso A/F sensors on amazon.

Denso 234-9007
http://www.amazon.com/Denso-234-9007...=pd_sim_auto_2

Denso 234-9005 Oxygen Sensor
http://www.amazon.com/Denso-234-9005...=pd_sbs_auto_4

Any ideas which one I need. The car seems to run fine though. Thanks.

lexus114

The Oxygen Sensor is the one after the Cat. So,I would think you want the top one. Thats confusing the way they listed those.

weinkaufjr

I have read several threads and came to the conclusion it was 234 9009. Hope I am right because I just ordered a couple.
http://www.amazon.com/s/ref=nb_sb_no...9009&x=18&y=15

Lexmex

P1155 is bank 2, sensor 1, that's the one visible when you open the hood right behind the radiator and off the of the exhaust manifold. That one would be 234-9009.

https://www.clublexus.com/forums/rx-...el-sensor.html

wvuguy

Thanks. I will order it tonight. I read some posts about many people having a hard time removing it. I sprayed liquid wrench on it a day before attempting to remove. Then while the engine was still hot, I was able to remove it using adjustable wrench and tapping the wrench with hammer.

code58

That's a really great price now isn't it? Seems like with the SOFT economy, it continues to go down. I paid about $162. ea at the dealer (Toyota) about 3 years ago and that was about as cheap as the net with postage. I did ask if they could meet the net price and they came close with the shipping on the net price.

Hatchman

That is a great price, I paid $113 only a few weeks ago for it.

wvuguy

Yup thats definately a steal. A/F sensor changed in around 100 bucks is not bad at all.
I have attached the image of the old sensor. The treads are pretty messed up. Hopefuly the treads on the exhaust manifold are ok.

code58

From the looks of those threads I would definitely see if I could borrow a tap somewhere and clean the manifold threads up. You definitely want the A/F sensor to go all the way in and seal and you don't want to mess up the threads on the new one. If you have ANY leak past the threads it will mess up the reading. If you're not used to using taps (or dies), you know that you want to lube the threads well and only turn in about 1/8-1/4 turn at a time and then back the same out, then go beyond about the same and then repeat the back-up. That way you don't destroy the tap threads and it cleans failed threads, rather than galling them. At the very least, you can take an old spark plug with good threads and take a die grinder with a cut-off blade and cut spiral groves in the direction it screws in and creat your own "poor boys tap". That will be softer than the tap, so be careful to let it do the job, rather than damaging it more. I have done this many times when I have buggered threads and not a tap handy to do the job. Done right, it works well. Good Luck!

wvuguy

I will give it a try. I am afraid some of the shavings might fall into the manifold. Can it cause any damage? Thanks.

weinkaufjr

You may want to try a thread restorer rather than a cutting tap to clean up the threads on the manifold. A cutting tape will remove more metal and that usually is not a good idea.

code58

Use some heavy grease on the tap to catch the debris and when you're done, clean the grease with some sensor safe cleaner. I don't think there's gonna be enough to even worry about, that's your exhaust so things are on their way out. You're not gonna be producing shavings actually, because you're cleaning the debris out of the threads and straightening the threads back up, it's not like when you cut new threads. The poster above me has a point about using a tap, but a tap is tapered and you only want to go in far enough to clean the threads of the transfered metal and rusted burned galled metal, you don't want to "bury" the tap because then you will have ended up with a hole that's to loose. Just far enough to "clean", not CUT. Common sense may not be so common, but it does work! I have thread chasers but I don't ever use 'em because they're too soft (they are professional Mac) and the burned, rusted and galled transfer left behind has been turned into granite and will often only laugh at a thread chaser.

wvuguy

I tried to look for thread chaser or tap and die locally but pretty much all of them were too small. Any ideas on the size? I will have to order online. Thanks.

weinkaufjr

Thread is 18, 1.5. Sometimes referred to as an O2 Sensor Thread Chaser. I though they were common at parts store but here is Amazon. I was glad I got it, very handy to remove some broken thread from the old Sensor that stayed in the manifold.


http://www.amazon.com/Oxygen-Sensor-...9763094&sr=1-3

wvuguy

I went to advance auto parts the guy told me they did not have anything. May be he did not know. I will check again tomorrow otherwise I will order online. Thanks.