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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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#176 ·
I think I found the issue...I hit a fire hose on the interstate a couple weeks ago, but never had a chance to look at it until now. Essentially, my exhaust was mangled when I hit it and almost completely closed off. I'm very surprised there wasn't a bigger issue. Would this cause a high voltage reading?

Pictures to come. Just finished pulling out the exhaust.
 
#177 ·
here is the destruction. think it's the cause?








On top of this, it broke a couple seemingly insignificant welds around the underbody panel in the front. I can post pics of that if anybody wants as well. Let me know your thoughts.
 
#179 ·
Wow. Sorry to hear and see that, that kinda sucks. Anyways, believe you have a wiring issue with your B1S2 or its damaged. Here are the only causes for DTC P0038:

•Faulty Bank 1,2 HO2S (Heated Oxygen sensor)
•Open in the heater control circuit (12 volt PCM controlled systems)
•Short to B+ (battery voltage) in the heater control circuit (12 volt PCM controlled systems)
•Open ground circuit (12 volt PCM controlled systems)
•Short to ground on heater control circuit (On PCM ground controlled systems)

So, either the wiring isn't making good connections or the wiring got jostled. Its definitely ok to drive. Maybe BlacksportD will chime in here.
 
#182 ·
Okay, great. I'll check it all either tomorrow or Friday. I didn't solder it the first time around because I didn't have time and of course I can't solder it now because I'm out of town for the holiday. I'll repost after I check that out and thanks for all the info.
 
#184 ·
Just remembered I have my exhaust pulled out, so I won't be able to check for a CEL until I have that replaced, HA. Still in search of a b-pipe...

Anyway, Happy Thanksgiving!
 
#185 ·
I replaced the b-pipe and put my stock exhaust back on and the CEL is gone. It looks like that pipe nearly being closed off actually was the problem. I didn't even end up touching any wires. I'll report back if anything changes and thanks again for all the help and input.
 
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#187 ·
Well, after close to 1000 miles of driving in the clear without a problem, the same P0038 code came back. Very strange. It looks like I'll have to go in and check all the wiring.
 
#188 ·
The car sat around for about 3 days and the CEL is gone again. Both times the CEL popped up was the day after long drives, 250+ miles (coming home for both Thanksgiving and Christmas). It's very strange that the code never came up any time I have driven the other way. Would long drives have something to do with the CEL and letting the car sit for a period of time be some kind of solution?

The thing is, the first time the CEL appeared, it stayed until I swapped out the damaged exhaust pipes, even though the car sat for a long period of time in that situation as well. The CEL was there, 30 mins later when everything was swapped out, the CEL was gone.

The whole thing has gotten me pretty confused.
 
#191 ·
I have been looking around and havent found a thread with a problem similar to mine so if there is please guide me in that direction.

with that being said.. I just picked up an IS200 a couple days ago. i dont know much about engines, but I picked it up for dirt cheap because the guy is military and he was PSCing in a couple days. The previous owner said that the CEL was on because of a bad o2 sensor and might be causing a misfire because it was running too rich or something along those lines. the car definitely seems to be running slightly off and seems sluggish. when its idling it smokes very slightly.. almost unnoticeable. yesterday i started it up and it ran for about 10 seconds and died. but thats the only time it has done that.

does this sound like an o2 sensor problem to you guys? i'm not so sure. like i said, if i'm in the wrong section of the forum please point me somewhere else. thanks!
 
#194 ·
Didn't see this thread when I had an issue...

I just fixed my bank 2 sensor 2 and now another sensor blew.
Is it normal for them to go in pairs (B2S2 AND B2S1)? And should I expect the other two to blow out also?

Also are the part numbers up to date? I want the original replacement (had bad experience before and don't want the headache)

Great write up btw! Thanks ahead of time.
 
#199 ·
Sorry, but my head is spinning from reading in circles about this issue. I am hoping someone may simply be able to tell me how to fix this and save me from another 3 hours of reading.

My issue: P0430 B2S2 - catalyst efficiency below threshold
Action: Changed the O2 sensor with a brand new, direct fit Denso.
Result: No change. Same CEL
Reaction: took car to smog station for test
Result: it blew as clean as it did when it was new. Even the smog guy was sort of blown away by how good the results were.
Assumption: Cat is working.
Assumption 2: either I got a bunk Denso sensor (very rare) or there is some other issue with the ecu or the signal the ecu is getting.

I am going to check continuity and such today to make sure there isnt a short or anything. However, after seeing all the info regarding this code giving people fits, I got worried that this may be quite the gremlin I could spend a lot of time chasing.
This car is totally stock, 110k miles, runs perfectly, gets good fuel mileage etc.
Just the damn CEL will not go away. Been rest many times both with scanners and with disconnecting batteries.

Praying for an quick answer!!

J.
 
#200 ·
"The P0430 is a fairly straight forward code pointing to a failing Catalytic Converter (in this case, the converter for Bank #2). The Oxygen Sensors measure the amount of emissions in the exhaust going into, and then out of the covnerter. When they see the converter is not "cleaning" the exhaust enough to meet specs, the converter is deemed "below threshold", the P0430 is set, and most commonly, the converter will need to be replaced."

From what I understand the issue is not with your o2 sensor but rather with the cat converter. Not sure how it could have given you a clean run with that error (which you got even after resetting the ECU).
Maybe Jason will give you different info on this. Good luck!
 
#202 ·
So assuming I still dont find any leaks, I get good voltage signals from the O2 sensor, could there be an issue with the ecu?
If I measure voltage on B2S2 and B1S1 and they are relatively the same, then I can only assume the issue is in the ecu?
Is idle a sufficient enough test to read voltage on these sensors? Or do I have to drive it?
 
#203 ·
Well you always want to do any oxygen sensor testing while the car is in closed loop, meaning it is fully warmed up and the signals to the ECU are more accurate. The voltages should be close but the main thing you're looking for is the fluctuation of voltage under idle, partial throttle, and WOT. I do not think it is an ECU issue, especially if you can hook up an OBD2 scanner and read the voltages on both banks.

Again, make sure there is no leaks, that's what I'd verify first. Then see what a scanner reads.

There are also other tests that can be performed on the cats aside from visually(which requires removal usually). IR temperature scans of the input and output of the cat can be done, the output is always a few hundred degrees hotter. Vacuum pressure tests can be done as well. I would check all angles before investing in replacement cats.
 
#205 ·
Sensor 2's need to run below 0.6V or the "Catalyst Efficiency Below Threshold" code will be set P0420 or P0430.

A nice trick is to throw a diode in the BLUE signal line. They use a 3A Rectifyer Diode from Radioshack. Install with the grey stripe away from the sensor. It drops the voltage signal about (0.2V) hence tricking the ECM into thinking the cat is burning more oxygen than it is.. it works.

Check out this link:AudiWorld Tech Articles
 
#206 ·
^^just keep an eye out for any glowing red cats:lol:

I think the proper way would be to replace the cat because it is no longer removing hydocarbons, carbon monoxide, and Nitrogen oxides efficiently. Back pressure will usually start to increase significantly if it's a collapsed honeycomb, performance will decrease. Therefore, you're still going to fail a SMOG, but you won't have a CEL. Just use caution if you're skewing the cat's monitor signal.

Interesting find though!
 
#207 ·
This is a headache!! I too have code P0430. I have so far checked three of the four o2 sensors. Two are bad according to Ohm readings. I will check the forth one tomorrow, I recently purchased this car and need to smog it. I just dont want to keep throwing money at the problem. Has anybody had the same code and not needed to replace the cat?
 
#210 ·
If you have a tap and die set you can chase the threads or an exhaust shop can do the same. If it's that bad, they can weld on a new bung and close of the existing or depending on how good they are, you can lay a bead of weld on the bung threads and drill and retap it.

I've even heard folks using a spark plug helicoil kit, but if you go that route, don't use any silicone based sprays when cutting the threads because you do not want it on the sensor.

I believe the threads are M18 x 1.5, make sure to use antiseize on the new sensor. Something like this will also work if the threads are partially stripped.

All i can think of atm, good luck!

 
#209 ·
I havent had the 02 sensor error pop up now in 5 tanks of gas....The only difference. I switched back to non-ethanol gas. My mileage also went from 16.5 to 20.5....But im sure that has nothing to do about it... :rolleyes: . The more I see about ethanol gas, the more I see it is choking our engines.
 
#213 ·
Thanks a lot
I appreciate all your input & time towards my situation.
I will first see if I can unscrew the o2 sensor fully after heat or spraying it. Then I can determine the condition of the bung threads. But what if I got the old o2 out and could not install the new one due to the situations we mentioned. I would have to still drive my car. What willl happen if I do drive with the sensor out fully and open bung?
 
#214 ·
No problem, anytime:)

That's why i would have an exhaust shop do the work. They can extract it there and install a new one as well as have the nessesary tools available like the ones i mentioned. Otherwise with no primary O2 on bank 1 the car will probably stumble and run rough as well as through a low voltage code. You don't want the O2 to be just hanging there and then you have go get a tap or run to an exhaust shop. I guess you could hold it in the bung if you have some tye wire or baling wire to wrap around it and the sensor to get you to a shop. It's either going to come out fine with a lil heat and lubricant, snap off in half, or mess up the bung threads. I'm pretty sure if it was about to snap off it would have when he tried to retighten it. So, you might be ok, may just need some heat and at most re-tap the threads if needed.
 
#217 ·
Just a update, i brought my car to a local muffler exhaust shop to get out the stubborn stripped bung of b1s1 and replace my new one.
He had to take a torch to the o2 sensor and bung heating it up red hot, then he cooled it with water. Did this twice, in order to effect the stripped threads i assume. Then i watched him re-tap the b1s1 bung, he was able to install my new denso sensor. I have no cel and i hope it stays that way. I was charged $90.00 which i think is fair ? especially for nyc area where everything is expensive. Im glad he was able to re-tap the bung rather then dropping the exhaust manifold out to weld in a new bung.
Thanks for your help throughout this issue Jason.
 
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