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Hi,
When using obd scanner Im not getting any reading from the oxygen sensor that sits before catalytic convertor (H2OS [B1/S1]). I do get normal reading from the oxygen sensor that sits after the catalytic convertor (H2OS [B1/S2])

I tried 2 OBD scanners with same results.
No check engine light at all , but I do get high LTFT values (15%-22%) - Lean engine reading, on the scanner.

Does anyone has any clue why I cant read that sensor values ?
 

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Is the 02 sensor connected? You might check the plug and wiring. I have never seen even a bad sensor that would not give a reading. My only other thought is, replace it with a known good sensor and see. Or you might have to get a wiring diagram and do a pin out check of the wiring from the ecm to the sensor. I would do the wiring check 1st. If a scanner is not reading a sensor, probably a wiring or ecm problem. Hopefully this guides you in the right direction.
 

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Howdy and welcome to the forums!!
Maybe a new sensor is in needed. 🤔

 

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Discussion Starter #4
Is the 02 sensor connected? You might check the plug and wiring. I have never seen even a bad sensor that would not give a reading. My only other thought is, replace it with a known good sensor and see. Or you might have to get a wiring diagram and do a pin out check of the wiring from the ecm to the sensor. I would do the wiring check 1st. If a scanner is not reading a sensor, probably a wiring or ecm problem. Hopefully this guides you in the right direction.
Thank you for the answer, I just checked the sensor. it is connected, I measured the electric resistance over the heating element as the Kia guide suggests and it shows 4.8 ohm vs max 4 ohms as written in the specifications. I dont think this is the reason.
The strangest thing as you mentioned, I get no reading from this sensor, not at all as it just does not exist. I should have got a "check engine" light or error code from the computer if the sensor malfunctioned, but i just get nothing. No errors at all. do you have any Idea what is happening here ?
the LTFT value is also quite high and I wonder how high is should be to trigger an error code in the computer ?
134895
 

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Hi,
When using obd scanner Im not getting any reading from the oxygen sensor that sits before catalytic convertor (H2OS [B1/S1]). I do get normal reading from the oxygen sensor that sits after the catalytic convertor (H2OS [B1/S2])

I tried 2 OBD scanners with same results.
No check engine light at all , but I do get high LTFT values (15%-22%) - Lean engine reading, on the scanner.

Does anyone has any clue why I cant read that sensor values ?
Hi benoved, I was curious if you are the original owner? If so, you should still be under 5 year bumper to bumper warranty. I honestly would not "mess" with this and risk voiding the warranty if things go south.

If you aren't the original owner, nevermind ;)
 

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The fuel trim ,short term should be constantly changing as it attemps to be zero. Long term, your reading is showing extremely rich. I would get a factory shop manual to see what the pin out is for that sensor. It should have a step by step trouble tree to diagnose it. In other words, step 1, check a, if normal, proceed to step 2. 1st possibility, bad sensor, 2nd, possibility bad wire going to ecm, 3rd possibility, bad ecm. Are the other o2 sensors constantly changing voltage after engine is fully warm? Drive the car with scanner connected. Are all other readings normal? Not only o2 sensors, all readings. If any other readings are not normal, I would suspect ecm. Hopefully this helps. I'm a retired auto tech. From experience, some drive ability problems can be a pain. Just go step by step and you will figure it out. Does your scanner only show generic readings or does it have the ability to use vehicle specific readings? Does your cel light come on when the key is first turned on. Not started, just on position? Make sure cel light works.
 

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Clarification, when ltft reads just a number, that is positive = rich. When number is - indicates lean.
 

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Discussion Starter #8
Hi benoved, I was curious if you are the original owner? If so, you should still be under 5 year bumper to bumper warranty. I honestly would not "mess" with this and risk voiding the warranty if things go south.

If you aren't the original owner, nevermind ;)
I am the original owner, and I will take the car to the dealership, but I have some experience with dealerships and I dont trust them. I want to be as educated as possible in the subject before I will take the car there.
 

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Discussion Starter #9
The fuel trim ,short term should be constantly changing as it attemps to be zero. Long term, your reading is showing extremely rich. I would get a factory shop manual to see what the pin out is for that sensor. It should have a step by step trouble tree to diagnose it. In other words, step 1, check a, if normal, proceed to step 2. 1st possibility, bad sensor, 2nd, possibility bad wire going to ecm, 3rd possibility, bad ecm. Are the other o2 sensors constantly changing voltage after engine is fully warm? Drive the car with scanner connected. Are all other readings normal? Not only o2 sensors, all readings. If any other readings are not normal, I would suspect ecm. Hopefully this helps. I'm a retired auto tech. From experience, some drive ability problems can be a pain. Just go step by step and you will figure it out. Does your scanner only show generic readings or does it have the ability to use vehicle specific readings? Does your cel light come on when the key is first turned on. Not started, just on position? Make sure cel light works.
the ltft are moving from 15% when driving to about 22% when idle. truning the ac on also get it to drop by 2%.

There are few pages in the service manual but i couldn't make much out of it :
here are the wiring of the sensors:
and here is a waveform, I actually see higher values of about 0.7v for the down stream sensor as oppose to what the waveform for this sensor shows which is about 0.4v. the upstream data sensor cannot be read with the obd scanner.

I will try to follow your advise and check other values
Thank you for the detailed answer.
Leo
 

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You are welcome. Possibly could be a dead o2 sensor. Don't know how much they cost for kia. Might try that if they don't cost too much. Also called air, fuel ratio sensor. Whatever you do, do not buy a universal sensor, waste of money.
 

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I looked at your wiring pin out, but I have a phone and it was so blurry I could not tell much from it. I could be wrong, don't want to make you waste money, but, if it were mine, I honestly believe I would try a new o2 sensor. There are some stores that will let you return parts like that. Might check and see.
 

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Discussion Starter #12
I looked at your wiring pin out, but I have a phone and it was so blurry I could not tell much from it. I could be wrong, don't want to make you waste money, but, if it were mine, I honestly believe I would try a new o2 sensor. There are some stores that will let you return parts like that. Might check and see.
Thank you,
I just recorded a file with all obd2 parameters while driving. the Catalytic temperature reaches 1500 F , seems too high isn't it ?
 

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I took the car to the dealership and they diagnosed a problem with the injectors. they replaced all of them and it seem that everything is back to normal. I scanned it again and the ltft are back to normal ~2.5% at idle.
for anyone interested, im attaching the diagnosis and repair summery. I would love to read any input you have on it.
135077
 

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As a general rule, air-fuel ratio and 02 sensors do not fail often. They tend to indicate other problems such as poor grounding.

@OP: Did you get an error code? If one of your 02 sensors has failed, it should show up as an error code.

Must admit that I am surprised that an issue with the injectors would prevent an air-fuel ratio sensor from working. But if the dealer replaced the injectors under warranty, and everything is working better now, terrific.
 

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Discussion Starter #15
As a general rule, air-fuel ratio and 02 sensors do not fail often. They tend to indicate other problems such as poor grounding.

@OP: Did you get an error code? If one of your 02 sensors has failed, it should show up as an error code.

Must admit that I am surprised that an issue with the injectors would prevent an air-fuel ratio sensor from working. But if the dealer replaced the injectors under warranty, and everything is working better now, terrific.
I had no error code. I did manage to get reading from the second o2 (down stream) sensor but not from the first (upstream). I asked the technician at kia, and i was told the the first o2 sensor require a special equipment to read its data.
both o2 sensors was diagnosed by kia and found to work ok.
 
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