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Oxygen Sensors - FAQ

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#1 · (Edited)
WHAT ARE THEY AND WHAT DO THEY DO?
OXYGEN (O2)SENSORS: Diagnose and Replace

WHY DO I CARE?
Typical scenario is that you get the odious CEL.

Instead of posting, "oh noz I gotz a CEL" (or for you Westcoasters "oh noes i has a CEL"), you run to the auto part store, borrow the OBD reader and get your code read. You write it down, then search here with that code.

NOTE: Your error code may not be O2 related.

WHAT IS THIS OBD YOU SPEAK OF, TELL ME MORE?
What Is OBD?

WHERE IS THE OBD PORT ON THE IS300?
Directly under the steering wheel, you will feel a port with a cap on it behind the knee panel. It is the white thing in this pic below.



WHERE ARE THE ACTUAL O2 SENSORS LOCATED ON THE IS300?
The IS300 has 4 oxygen sensors, named B1S1, B1S2, B2S1, and B2S2.

Bank 1 (B1) refers to the first bank of cylinders or 1-3 (first three as you look at it from the front) Bank 2 (B2) is the second bank of cylinders 4-6 (back cylinders closest to the fire wall).

Sensor 1 (S1) is the first sensor in the particular bank (1 or 2) in the path from the engine block and out. Sensor 2 (S2) is the next one in-line.

B1S1 should be the first one you see as you look in the engine bay. It is up high, and toward the front. The one below that is B1S2.

B2S1 is near the firewall. The one under the seat (under the car) on the Y-pipe is B2S2.

Sensor 1s are "pre-cat", and check A/F mixture, Sensor 2s are "post-cat" and check catalytic operating efficiency.






Thanks to digger08 for the below pic.




WHERE CAN YOU BUY THEM?
Dealers, of course. Your local auto part store sells generic ones, but most likely they will need to be spliced in. Most people swear by Denso since those are OEM. Generic ones are cheaper, but of unknown quality, and do not just "plug" in.

Here are some online sites, you can get a Denso 02 Sensors: Denso starters, alternators, iridium plugs, fuel pumps and glow plugs, OELEXUSPARTS.com, or Sewell Lexus Parts and Accessories Online - All Genuine Lexus Original Equipment Parts. They are all around the $100-$150 neighborhood with shippine. Generics can be as much as half that amount.

WHAT ARE THE PART NUMBERS?
If somebody knows the part numbers can they post them up? I think they may have multiple numbers as well. Double check with the seller before you pull the trigger, also report back if they are right or wrong.

Here is what I have heard, these are not 100% confirmed. (* = slightly confirmed, ** = pretty much confirmed)

Bank 1 Sensor 1:
89465-53090 (2001) *
89465-53140 (2001) *
89465-53210 (02+) **

Bank 1 Sensor 2:
89465-53110 (2001) *
89465-53200 (02+) **

Bank 2 Sensor 1:
89465-53110 ?
89465-53200 ?
89465-53190 (02+) **

Bank 2 Sensor 2:
89465-53120 (01) **
89465-53190 (02+) **
89465-53150 ?

HAS ANYBODY DONE A DIY YET?
Yes you are in luck, as long as you need to fix B2S2. It will at least give you a general idea of what is involved as well when replacing an O2 sensor.

http://my.is/forums/f115/diy-p0161-o2-sensor-b2-s2-change-pics-263613/

WHAT IF I JUST GOT A HEATER CIRCUIT MALFUNCTION, DO I NEED TO REPLACE MY SENSOR?
No, you can bask in the yellow glow of your CEL and leave it alone (does not effect drive-ability), or you can do the following work-around.

http://my.is/forums/f88/how-fix-p0161-o2-sensor-heater-circuit-malfunction-b1s2-free-p0141-290038/

WHAT IS THIS 02 SIMULATOR I HEAR ABOUT?
By way of installing headers you are removing your catalytic converters to increase flow. By removing your cats, your B1S2 and B2S2 oxygen sensors will tell your ECU that something is wrong.

An 02 Simulator will give the ECU the impression that everything is A-OK with B1S2 and B2S2, and your CEL will not shine.

This can be a route to consider if you don't have headers but a B1S2 or B2S2 goes bad, as an O2 simulator is cheaper than a new O2 sensor. Remember these sensors only detect how well your cats are working, they do not effect drive-ability or performance.

http://my.is/forums/f88/how-install-o2-simulator-284733/

http://my.is/forums/f88/o2-simulators-dummies-336947/

ALRIGHT I'M READY TO CHANGE MY O2 SENSOR, WHAT DO I NEED TO DO?
Wait to your manifold is 100% cool, unclip it and hit your sensor threads with some PB Blaster. Let it work it's magic. Then use either the special 02 socket (has a slit in it) or just a normal 22mm wrench, and unscrew it.

Get your new 02 sensor, dab a little anti-seize on the threads. Make sure it is O2 safe anti-seize, you don't want to ruin your brand new sensor right away.

Screw in your new sensor and make it a little more tight than your oil drain plug, but not too tight. Then clip it in.

If you have any other tips, info, pics, or links post them up.
 
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#220 ·
i got a code for p0420 which is "Catalyst System Efficiency Below Threshold (Bank 1)" ive seen conflicting info on this some saying this code means you def need a cat cat, other say its just a bad o2 sensor. which o2 sensor would it be if it was an o2 sensor and can you visually inspect an o2 sensor and see that its bad?
 
#222 ·
I recently replaced b1s1 b1s2 but forgot to disconect battery! Ran car for a few min still felt hisitant then I remembered and took the neg cable off for 5 min started car back on and it seemed proper. My question is could I have mayb still ruined an o2 sensor cause of this? If so could how can I find out which one with out obd since there is no check engine light on.
 
#226 ·
All that anti-fouler does is keep the exhaust flow out of the oxygen sensor's path. So it may work to keep efficiency codes away, it may not. The best route is Tokensolutions full PNP O2 delete, takes care of the sensor and it's heater so you can eliminate all post cat sensors. They're a vendor here, check em out. I believe they are back in stock or going to be very soon.
http://www.tokensolutions.net/plug-and-play-full-o2-delete-lexus-is300-mkiv-supra/
 
#225 ·
I lol@ the word fix.
 
#228 ·
what's so funny about it? yea it's a problem once check light comes on and u r doing 5 miles per gallon, and yes then it's becoming a problem which I should "fix"
Fixed.

Neither post cat sensor will cause a MPG loss. Unless you have a catalytic converter that's partially clogged up, creating too much back pressure. In that case you may have much bigger problems if the car is only doing 5MPG. Do NOT use those foulers before the cats, your primary oxygen sensors, only on post cat. Again, go with the TS PNP delete.

I think a better word for fix here would be "simulate" lol.
 
#229 ·
Hi all, after some advice really, I am going to get a Lexus is200 sport, have found a really nice one but the ad says this and was wondering if this is viable or could it be a cover up for something more serious? Cause have read that if there is faults with the air sensors then the car doesn't run correctly.

"one minor fault the air intake sensor is no longer working and will need to be replaced not essential as it does not affect the driving of the car what so ever they are 40 pound to buy and it is easy enough to do just 2 clips"

Please help.......
 
#231 ·
I just ordered a header and y pipe. Do I have to plug the B2S2 AND B1S2 back in ? Literally unplug them completely till token has the o2 delete instock? If I have a cell that is fine but will it hurt/ affect driving the car?
 
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#232 · (Edited)
You can unplug both B1S2 and B2S2 with no problems or effect on performance besides a CEL. Those two sensors only monitor cat performance, that's it. But I would probably wrap the O2 harness connectors with some tape to protect the connector until you get your delete if you remove the sensors. Although, if there is spots for both sensors and you don't want a CEL, a couple of anti-foulers from the local parts stores should keep the CEL off(with B1S2/B2S2 installed). That's up to you.
Fyi, BlackSportD says he will have a new batch made mid February.
 
#233 ·
Could an o2 sensor throw these codes: ( I have aftermarket exhaust system)

P0420
P0301
P0304

these last two codes are misfires but could they be caused from a poor air/fuel mixture? are they unrelated via o2 sensors and dont they run off different coil packs??
 
#236 ·
I have cel codes p0420 and p0430. I was wondering if I need a new catallyc converter. Or just need the sensors replaced. Will changing my cats fix my sensors problem and shut the cel off for good? Will I be able to use the same sensors on my new cat converter? Or would they still need to be replaced? Please point me in the right direction I just want to pass inspection and have my baby running healthy. 143k mile 2002 is300
 
#242 · (Edited)
The pic no longer exists, I even tried searching too. However, I found the pin outs for 02+ and can easily walk you through the mod. Here's the pin out.

**what you do is cut B2S2 red/white stripe heater wire before the ECU. Leave yourself enough wire so that you can splice the remaining red/white stripe wire that goes to the ECU(which is now just a pigtail wire off the ECU connector) to the green/black stripe B1S2 heater wire(this is an inline splice, so the ECU will sense B1S2 and think B2S2's heater circuit is ok because the red/white stripe wire is spliced into it). Then you can just tape up the red/white stripe B2S2 wire that you cut which came from B2S2. Hope that helps and makes sense, lemme know if not.
 
#243 ·
Having some trouble finding the right part numbers for my o2 sensors. I want an aftermarket set, was quoted $324 for the two I need at the dealership. Please help me to identify the correct aftermarket part numbers. Was looking into Bosch. If there are some better alternatives, please advise. Thanks!

2003 IS300:
Bank 1 Sensor 1
Bank 1 Sensor 2
 
#244 ·
Well I finally got round to replacing one of my O2's (B1S1) with the Denso part 234-4209. The wires color codes matched up fine. Note the Denso has crimp connectors in the box, When I tried to solder I found out the wires do not solder well, the wires do not want to wet and are probably not a copper alloy.
So just crimp them in to the original harness.
 
#247 ·
I would be careful with the simulators. I had one on my car for years and it worked fine. I had actually forgotten that we installed it. My car recently needed some major repairs (cats and new O2 sensors) and that simulator caused a lot of confusion. It caused the computer to keep throwing O2 sensor codes after all the sensors were replaced. The shop couldn't figure it out. It wasn't until I was looking around here and saw some posts about the simulator that I remembered that my car has one. I thought it was a long-shot, but told the shop about it. After the removed it, the last code cleared. They "shamed" me telling me that I could have ruined my computer...and I am $2200 poorer and spent 10 days without a car. I suspect given the age and mileage of my car, the cats needed replaced anyway, but the extra trouble cost me an extra $600. The O2 sensors are relatively cheap...not much more than I recall paying for the simulator. I wish I had been smart enough years ago to replace the sensor, rather than put the simulator on.
 
#252 ·
Denso. Autozone is always overpriced I've found. Amazon or Rock Auto is your best bet.
 
#257 ·
I think it should be noted that on both banks, sensor 1(precat, upstream) is the one that will effect performance. B1S2 and B2S2 (post cat, downstream) really only need to be replaced if you live in an emissions county.

Also, when it comes to getting these little b****** off, PB Blaster seemed to work wonders. Also, my local Autozone had a o2 sensor socket set that they rented out to me. This made it super easy for me. Especially B2S1(beside firewall).
 
#260 ·
If you can wait a few days, order from Rock Auto, https://www.rockauto.com/ Then enter Brand, model, year etc. The daily driver section has many brands. Denso and NTK/NGK are OEM for Lexus/Toyota and other Japanese brands. They are priced from $50-67.00. It is important that get you exactly what you need. your code reader will tell you the bank 1 or 2 and sensor number 1 or 2. The prices from Rock Auto are the best. Look for a 5% coupon on the internet. It is important to check the connector for the perfect match online. Double checkRock Auto has a wide shot and closeups in the info section. Warning, don't open the plastic package until your sure it matches the connector of the unit taking out. It is not returnable if opened. You will need a 02 special socket. Pull negative ground off the battery. Read all the valuable information on the forum. Look at Squareback the first for the photo. That is the best illustration you can have. Look at Chrisfix on youtube:
 
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