carguy07

I would not bother with B1-S2 unless it is throwing a code. Does not effect how the car runs at all and might not come apart and go back together as easy as the A/F sensors.

salimshah

Excellent advice, if it is not bad, dont mess with it.

Salim

artbuc

+1!!!!!!!!

01rxwhite

Well, enough said, guys. I won't replace it if it's not coding. If that O2 sensor doesn't affect the engine performance, then what does it do? Mainly an emissions thing? We don't have an inspections law in Alabama, so I suppose I could pollute air without knowing it?
The engine is running really smooth though since replacing the B1-S1. The verdict is still out of the effect on the MPG.

I am lost! If there is a problem in metering, you will get Check Engine Light and code(s). If the CEL is not lighting up, you dont have emission related problem.

Salim

BobWATL

This post is simply to share some of my experience in replacing my oxygen sensor in my '96 SC300 recently and to thank all those prior postings which greatly assisted me in having confidence to do this job myself. I know that I saved hundreds of dollars by doing this fairly simple replacement because of my reading all the posts here and following some actions taken by posts described here. I went to Auto Zone for a free scan reading of my check engine like. I purchased the Denso replacement sensor for $53 and an OBDII scan reader for $30 from Amazon. I purchased AB Blaster ($5) to help loosen the sensor from the exhaust manifold. I "borrowed" an oxygen sensor wrench from Auto Zone and easily removed the sensor. I paid for the wrench ($25)and returned it to Auto Zone undamaged for full refund (that is Auto Zone's apparent standard practice to offer free tool loans). So all in all, I paid less than $100 to complete this task when I had a quote from a repair shop of $100 to just diagnose the check engine light indicator. I have previously paid hundreds of dollars to Lexus dealership to do this very work. Thank you all for your helpful postings as I read each with great interest on this particular sensor problem. The posts with photos were especially helpful. Please continue this invaluable forum service.

gcimatt

Thanks to this discussion thread, I was able to change the firewall side A/F sensor in my 2000 RX300 (238,000 mi) in arout 30 minutes. The most difficult part of the job was getting the sensor unplugged from the wiring harness/boot. I had to have my wife come help me with that part.

I know that I saved over $150 doing this myself, and I was able to have the RX ready for a road-trip to my son's baseball tournament the next day!

You guys ROCK! Thanks for the great insight. I really enjoy reading through the postings on this board, and learning from all of your experiences with your RX's. This RX is my first experience with a Lexus, but I have really enjoyed it so far.

mikemacch

This is a great writeup, I read the whole thread and there was also some helpful tips added later. I haven't made up my mind as to whether I will attempt it, but if I do I am confident I have the information I need. Too bad I just gave away a great set of truck ramps 2 months ago while moving into a new home. I also gave away my ramps last year. I have to crawl under and take a look and see if it feasible. I just got a pair of po171, p1130, p1135 codes. The car hesitated today for the first time along with the codes, looks like the firewall sensor, intermittent now but soon will fail solid.

Has anyone seen hesitation when they get the p1135,p1130 codes?

frank1961

Hi I have un connected the eletrical connector for b1s1 sensor, but have trouble to remove the nut, is counter clockwise to remove it? tried with different liq like deep creep, pb blaster, and even try to start the car for 10 min. still doenst work, any idea?

Thanks

BobWATL

I can't remember now but I would almost be sure that the sensor unscrews with a counter-clockwise motion. My recollection is that I used the PB Blaster on the sensor connection the night before for an over-night soak and then again after I drove the car for a while the next morning but after another soak of PB Blaster and it unscrewed very easily. I think you have to let the manifold cool down for a while. And I think it helped me to have the right wrench to unscrew the sensor which I "borrowed" from AutoZone. Good luck.

john95134

Thanks for this great thread. Following the instruction I easily replaced B1S1 on my 2001 RX300 which has over 130K. One day later, however, CEL came back with code P1150 indicating problem with B2S1 (don't know why this was not reported before). Unplug the front sensor connector and the resistance reading is around 1. Does this mean the sensor is still good? Anyway I decided to replace it. Ordered another Denso sensor from Amazon ($100.45 with free shipping) which should arrive in next couple days. One question I have is that I noticed there is a clip/tie which ties the sensor wire to transmission dipstick tube, when I replace the sensor do I just cut it and use a cable tie to tie down the new sensor wire or this clip can be removed (I tried couple times but couldn't open it) and reused.

mikemacch

I was able to open it and reuse the clip. It ratchets together, you just have to separate the opening of the clip. You can use a tie wrap also shouldn't matter.

ReadyAct

I recently replaced the A/F sensor which is located under the truck. Went to O'Reilly's to see what code was producing the CEL and I had the dreaded P1135. Problem with O'Reilly's is they can't tell you how to fix the issue, but I was given a printout of about 20 possible solutions. But thank God for this forum and you guys I knew what the resolution was I just needed confirmation of the trouble code. I purchased the sensor from Amazon, click here for the direct link and had it at my door within two days (standard shipping). While waiting for the sensor to arrive I purchased the senor socket from AutoZone http://www.autozone.com/autozone/accessories/OEM-3-8-in-drive-oxygen-sensor-socket/_/N-26lc?itemIdentifier=47738_0_0_
As stated several times in this thead it takes some effort to get the old sensor to break loose. Before I ordered the replacement sensor just to make sure I could get the old one out, I had loosend the original sensor by turning it back and forth just to make sure I could get it loose. I was like hey this isn't going to be too bad so I tightened it back thinking that would help once it was time to actually replace the sensor with the new one, but boy was I wrong. Due to rust and dirt it still took a good bit to get the old sensor to turn all of the way out. I could move the old sensor back and forth and make about one full turn then it would get stuck. Since the old sensor was coming out some, but getting stuck on old rust/dirt I was lazy and just blasted a little WD40 in there not so much to leave a mess for the new sensor and then eventually I was able to get the thing out. I cleaned out the hole really well and the new sensor screwed in with little effort. I thought I pulled the correct fuses to reset the CEL, but for some reason once I started the truck I still had the same lights on. After driving about 10 miles I did a shutdown/restart and baaaaaaaaaaaaaam no lights. It's been two weeks and the truck runs like a champ without any trouble lights. So once again thanks guys!!!!!

Baetke

When using heat to remove sensors, remember that both the A/F and O2 sensors have internal heaters that are there to maintain their temperature at about 700 degrees. I you want to try and use engine heat to help loosen them up, remember to disconnect the electrical connectors before you start the engine. Otherwise they will probably warm up faster than the manifold, just the opposite of what you expect. This will probably throw some more trouble codes but obviously you can ignore them.

Hatchman

ReadyAct, glad the the info on here helped. I know it saved me a lot of money and troubleshooting, or an expensive trip to the dealer.

Just a tip, PB Blaster works ten times better than WD40 on loosening rusty bolts. It is truly an amazing product, and I can't believe I was wrenching three decades before using this wonderful product. It will wick down through the threads and break up carbon buildup and rust much, much better than WD40. Even better than Liquid Wrench.

ADKLEXUS

Good advice on this thread. I just did my AF sensors on my RX300 AWD. 172K. Sprayed PB on them two times two days apart and I was able to replace both of them in 1/2 hr w/o jacking up the car. Used O2 sensor socket on a breaker bar. They were definitely both bad. CE light was on throwing the usual AF codes. Happy to report fuel econ went from 16.1 to 23.2 mpg. Very pleased. Thanks to everyone on here who takes the time to help others out. Here's my tip:

stockwiseauto.com

DENSO 234-9009 Air- Fuel Ratio Sensor

88.67 each

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