Causes When Oxygen Sensor Replaced and Code Keeps Coming Back

Fixes when a changed O2 sensor code keeps coming back.
How to Test Catalytic Converter Video:
• How To Test a Catalyti...
P0171 Error Code Video:
• 9 Causes and Fixes for...
Be sure to check for other codes.
Posible Causes:
⦁ Oxygen Sensor Circuit
The Error Code Didn’t Clear
O2 Sensor Wiring Open or Short
Blown Fuse
⦁ Exhaust is Clogged or Leaking
Catalytic Converter Clogged
Exhaust Leak
⦁ Engine is Running Rich or Lean
Bad MAF Sensor
Bad Injector
Vacuum Leak
ECM/PCM Failure
www.backyardmechanic.org
By using this information user assumes all risk of use.

[@HappySox81_TheOriginal]

I replaced all my sensors and kept getting the same code. I tried everything. Then I watched your video. You stated exactly what the sensors designation was and I went to look. BAM…. 850.00 later and I could have just replaced the missing 15A fuse. You’re the man!!! Thank you before I would have taken it in somewhere and spent MORE money on it.

[@MusingsofaWanderingmind]

What kind of fuse was it?

[@cuarajhyrojayju4397]

My Mecanic told me the fuse have nothing to do with the 02 sensor

[@HappySox81_TheOriginal]

@@cuarajhyrojayju4397 it was a little tiny 15A fuse exactly labeled as this one said to look for. Under the hood. The fuse has everything to do with how the sensors work. Get a new mechanic.

[@oespelho2281]

Thank you, watching from Brazil.

[@monkey875]

I replaced both o2sensors and the light didn't go away, my problem was that connection was not plug in all the way, so I plug it and the light when off.

[@ua1881]

The plastic clip connection right? I tried pushing it in all the way and I feel that it might be my problem. I never felt a click and when I pulled it off it came off relatively easy compared to the one I replaced

[@debbymorden1902]

2013 Chevy Equinox...changed O2 sensor upstream & downstream.. 4K road trip was fine entire time...light back on..replaced both srnsors again yesterday...light back on today...its running great...

[@j.e.8120]

Maybe a fuse??

[@nifrios]

You ROCK! thank you so much for your clear and concise analysis of returning O2 sensor codes, very helpful🤘🏼

[@HiddenValleyHomestead]

Yeah but if its a clogged CAT then you'll get a downstream O2 sensor code as well! But the upstream sensor will definitely be a number of issues like you said

[@cbucchioni5215]

thanks for this--- I'll be checking all my fuses and such as he recco. Much appreciated

[@Flexx007]

Why is this video under watched and why wasnt this my first video suggestion for this code ..!?!? This is an excellect video of everything abt this code that i bave been through since having it lol

[@joev.7909]

Flex007 Basically it was ok except this video is suppose to be about a freaking p0038 code and NO OTHER CODE! This is a "heater side" issue on the O2 sensor. Yes wiring fuses relays can cause this issue but this can be simple to check just by plugging in a scanner and watching the "data stream" once you see the sensors working by see the numbers moving then you know the wiring and sensor is working. However one thing he didn't mention is if you DON'T have an OEM sensor then your sensor will not give out the right readings back to the computer needed to turn of your code. The other thing he said was that an exhaust leak can throw off the sensor reading which in the case of a leak after the catalytic converter wouldn't effect the downstream sensor. And you can pass inspection if you have all your exhaust pipes from the manifold including the cat. After the cat does not matter for inspection And if you had a leak before the cat your upstream O2 would be throwing a different code

[@worldpeace5853]

I got the cat changed last year for catalytic converter P0420 error on my 2016 CRV. 6 months down the line I got the P0139 error. I changed the downstream sensor this time. 2000 miles more I again got the same P0139 error. I called Denso and they sent me a new sensor because of warranty. I called the mechanic to reinstall the downstream sensor and he says P0139 error may be because of upstream sensor also and recommending to replace upstream sensor. I am so confused this is driving me nuts!!!!!!

[@cuarajhyrojayju4397]

2004 Infiniti fx35 after replacing 02 sensor the code keeps coming back and my Mecanic can’t figure it out I try to tell him to check the fuses and he tells me fuses have nothing to do with 02 sensor, he repaired vacuum leak and the code still coming back.

[@MarkConwayTheBurgerKing]

I have replaced upstream oxygen sensor on my 2006 Hyundai Elantra. Plus, injectors, VVT solenoid valve, map/MAF sensor, Purge Valve Solenoid, PCV valve. The P0133 still coming back. Normally at high speed. Only clue I have after smoke testing last week. Throttle body butterfly spindle shaft leakage Both ends. Will this throw off the Oxygen sensor on high speed deceleration?

[@robwhiff3411]

I have an iS 250 Lexus 2006 What about spark plug and coils could it cause p0138 ? I put a brand new map sensor and a brand new O2 sensor. and I also noticed a leak on the flange coming from the manifold to the converter. Fix it and still getting code…thanks

[@shauncunningham5088]

Thanks what a great video know your stuff and I appreciate it. Just want to say thank you. You have a great day

[@emcycles]

I have a 2000 Chevy Silverado 5.3 just replaced all four O2 sensors, gas cap fuel filter and another little chip plug-and-play deal on top of the fuel tank. I've reset the OBD2 service engine soon after each service and continues to come back. Along with my brake light and ABS light. It might be coincidental but all happened same time. Any ideas?

[@ramanpreciado2241]

Check vacuum leaks ( any air hoses on your engine that are leaking) also check your circuit. You pray to jesus it's not the catalytic converter.

[@robertsylvester3542]

I have 2010 Toyota Camry that won’t start after replacing the O2 sensor the upstream it will not start. It will crank but it won’t start. Somethings wrong. I definitely need help.

[@yashicasmith4274]

So i have a 2008 Honda odyssey and been getting the codes po155,po134,p2240,p2251. The oxygen sensors have been changed numerous times along with the catalytic converter, the codes keep coming back it's really been a pain in my side for the past 5 years I've spent so much money trying to get these codes cleared. What can you suggest?

[@cuarajhyrojayju4397]

I’m having the same issues, my Mecanic can’t figured out.

[@Dee--Jay]

If you replace the sensor on the downstream, what else could it be because I replaced mines but i still get a 0036 0141 code. I check live data. Its reading high, around 600-700 millivolts on the old and the new sensor. Plz help

[@thedebumdum8268]

My issue is that my 03 350z is having two p0037 code. I replaced the o2 sensor and replaced the fuse yet it’s still there. I unplugged and plugged back in the sensors hoping maybe I didn’t click em in right but still code is there so I’m lost now

[@5.0Licks]

I have Both o2 sensor codes and a P0302 Cylinder 2 code I swapped coils and spark plugs… my final guess is a clogged fuel injector/ and or fuel pump and filter. 2014 ford mustang GT (5.0)

[@Avvura]

My sensor was throwing a code and when i tested it, it seemed faulty. Ordered a new one, and it finally cleared the code until recently the check engine came back for slow response. Connection seems good. Not sure what else is causing it. 1133 and 0113 are my codes.

[@HeinrichEichmann]

My Accord V6 threw a P0130 code for an oxygen sensor but it was because I embarrassingly neglected the air filter for so long it was totally clogged. It's been 3 months and the light hasn't come back on.

[@kentgregg9331]

I had a 1,2,3 cylinder misfire and took out my downstream 02 sensor and was loud but ran with no errors. I then placed the suspected bad 02 sensor on the right(other) side and the codes followed to 4,5,6 cylinder. So I bought a new 02 sensor and replaced it on the right side and still getting engine bogging down on 4,5,6 - Any ideas what my problem might be?

[@veganninja5886]

I have a P2251 code on my 2009 Kia Spectra EX. I replaced the Oxygen sensor and exhaust manifold/catalytic converter but I still get this code and have low RPM's

[@marcelinanoss8825]

these O2 sensors are a major pain in the butt and I don't really see the purpose for them these days, In Ohio only 5 counties require E-Checks. Cleveland is no more a major factory-polluting city, Get rid of Echecks guys!!

[@patriciabanta2631]

I changed my O2 sensor on my ram 1500 the light engine turned off after but came back on the next day 😢

[@Ayvengo21]

How does this error appear usually ? I have this p0133 from time to time like once per month and then all goes normal again.

[@phillydee1004]

Get a diagnostic done, i had bad ignition coils so dont waste money.

[@ericrivera5354]

Thanks for the video, my obd2 scanner is reading that my o2 sensor is -2356ma any idea why is that?

[@jonathancritzer592]

So I've replaced the mass air flow box and o2 sensor and fixed the exhaust. It's a 2003 ford focus . Still doing the same code and running and idling weird but hasn't put a check engine light again?

[@maddogg26]

Possibly vacuum leak

[@toddhubbard7120]

Please explain if you would how an exhaust link underneath your truck or car can affect how the 02 sensors read the ambient air (outside air)(which now has exhaust fumes in it from a leaky exhaust pipe) would alter the downstream sensors ability to send the proper information To the computer Which has to make adjustments according to reading the downstream sensor is getting. Remember there's an exhaust leak under there. So the downstream sensor maybe the upstream sensor as well is confused.

[@jackcirrito3458]

I assume the leak would have to be BEFORE the 02 sensor like a cracked manifold.

[@shauncunningham5088]

Also I had a question for you. They said an autozone I had it found out what my codes were and I got APO 430, and I changed it. The 02 sensor bank 2 AM I supposed to change both of them on the right side. I changed the upper one I think I'm just gonna change the lower 1 also, just for s**** and get. Wasn't too sure thanks have a great day

[@scottsprowl7484]

I have been chasing the dreaded p0300...random misfire. We did a date scan and found a bad coil and a bad injector and the evap wasn't functioning correctly. Got all those fixed, truck ran great, the next day sluggish again, now I have a p1133 code.l and p0175 What the heck?

[@lisaalony415]

For us, after replacing two O2 sensors and still the same problem, thanks to this video -- it was a cheap FUSE!

[@thuanlu6838]

I have an Honda Odyssey 2009. I change the oxygen sensor bank 1 , the light still on. So I clear the codes and lights goes off. few days later lights on again. I scan the car with OBD2 and still have the same problem. Bank 1 sensor please help

[@HVAC_Mechanic]

If the 02 sensor is good, I would test the wiring next.

[@MrNext2000]

I replace all 4 o2 sensor and after that I get the code P0402 with I think is the bad catalytic but i was hoping for and answer

[@HVAC_Mechanic]

A P0402 code is an issue with the EGR valve "Exhaust Gas Recirculation “A” Flow Excessive Detected". Here is a video on it kzbin.info/www/bejne/gXLGknd7ob5-rrc

[@ericgrajeda2671]

My oxyg sensor new but light still on Engine light with the code maybe the intake need replacement?

[@cletosoto7771]

I have a 2016 Ford explorer XLT and i change Both o2 sensor the shop told me it was that but now check engine light turn on by putting my car in gear po161 code please somebody help me

[@blackcypher2834]

Another reason could be a POS aftermarket sensor. Bought cheap o2 for my Altima. codes kept on. Replaced them with OEM and the code went away.

[@Thibwe_dlo]

Could it really be it

[@everyusernameistakenomfg]

My mechanic has replaced my O2 sensors twice in the last 2 weeks and each time my car gets worse afterwards. It's after the first time he changed them, it started to hard idle and when I went to pull out in first for a second gear from a slowdown more stop the engine would sometimes sputter out and die. Pulling over turning the car off and turning it back on would allow me to get a gear and accelerate again. I'm at a loss for what's wrong, I don't know if they'll be able to figure it out and I don't think replacing the O2 sensors a third time will help. I feel stupid for getting them replaced once when all my issue before was just the check engine light really.

[@HVAC_Mechanic]

A bad 02 sensor should not cause the engine to run badly. The engine will not go into what is called a closed loop and be less responsive but should still run OK. I would look for other codes as there likely is another issue.

[@everyusernameistakenomfg]

@@HVAC_Mechanic I'll go to autoZone and have them look at the codes again. if it's still bad after going to the mechanic on Monday I'm finding someone else :( it's making a tinny rattling noise from the passenger side of the engine now too. All these weird symptoms only started after they messed with the sensors. The codes before they changed the sensor the first time were P0137 P2097 Secondary P2270 I would like to fix it myself but I am beyond amateur and wouldn't be able to figure out what's wrong with it :(

[@sandyking5984]

I have a p0420 talks about the two sensors. First says pending. Other says permanent. Please help!! I'm to go to my mom's 94 years old I'll. 8 hour drive!!

[@sandyking5984]

My son inlaw replaced from sensor n engine light still on.

[@HVAC_Mechanic]

A P0420 is a "Catalyst System Low Efficiency," which could be a bad 02 sensor giving bad data but can also be a bad catalytic converter; it needs to be diagnosed to fix the issue.

[@samlevine6357]

If the relay is bad will it make for low voltage code only 1 o2 sensor only?

[@adismujabasic2]

I have P2196 fault code on my Skoda Octavia 1.4 TSI 140hp, when I remove this code from ECU, every 5 to 6 days comes back. I replaced O2 sensor before catalyst, all spark plugs and one induction coil on third cylinder because I had a missfire fault code on third cylinder. I don't have any problem with power on car, no problem with fuel consumption( I have average 5 liter on 100km). If you know why I have every 5-6 days this fault code. Maybe I must to change all of inductive coils.

[@t.r.8386]

I jesili li rijesio taj problem?

[@jeremyhahn5593]

Hello i have a 2011 toyota prius i never had a check engine light on before it spun a bearing i replaced the engine and took all the sensors off the old engine and replaced it and the headgasket while i had the new engine out and i have a p0420 code so i then replaced the o2 sensor with an oem replacement part still has a p0420 code i checked all wires and took it to the stealership they charged me 250$ and told me that it was an intermittent problem with the 02 sensor so i then replaced it with another oem part and still have the same problem the egr cooler was almost completely clogged when i replaced the engine so i cleaned all parts with a pressure washer and welding wire but i still have this code any suggestions would really be helpful i dont know what else to do ..btw your video was very informative ty

[@HVAC_Mechanic]

It needs to be troubleshooted, but it sounds like a wiring issue, such as a bad connection or a wire rubbing on metal.

[@jeremyhahn5593]

@@HVAC_Mechanic I've had to replace the headgasket on the original engine when I bought the car for my wife (no check engine light ever on original engine) then she left her daughter drive the car she hit a curb and ran the car out of oil it spun a crank bearing so I got a jdm engine so while I had the new engine out I replaced the headgasket and cleaned the egr cooler and all the passages in the intake that were clogged with carbon buildup (was alot so bad the egr cooler was clogged almost completely and when I was taking the old engine out I had the valve cover off and when I pulled the engine I put it back on to use the hook on it for a chain and I had accidentally smooshed a wire from the harness in the valve cover I believe it was the temperature sensor wire so I had resoldered the wire that it crushed anyway I put the newly rebuilt jdm engine in and that's when the check engine light came on so I bought a cheap replacement from rock auto that didn't clear it so I got a Denso replacement that didn't work so I bought another one toyota replacement and took it to the stealership they charged me 250 for a diagnosis and told me that it had a intermittent o2 failure with p0420 code I was so mad because I already knew that so the sales manager called the tech and he said he checked the email and it wasn't in there they told me that for 700 they could diagnosis it further I told them I'd never let them touch my car again. The car runs fine I just don't know what to do I believe I checked the fuses but idk about relays and how they work

[@jeremyhahn5593]

Thank you so much you're been super supportive your videos are amazing and full of knowledge I just want you to know that what you do helps alot of people

[@jeremyhahn5593]

kzbin.info/www/bejne/i16wZnaLmNiWY6csi=5O9cK4UWOsSXUBLX

[@jeremyhahn5593]

Here is the link for the test light but im scared to try this method on my hybrid

[@jat-justamaturetech-philpj8285]

I keep getting po172 - po175 oxygen sensors running rich bank 1&2. After replacing my injectors grom 1 hole to 4 hole. I did a fuel pressure test. Put new fuel pressure regulator. Codes came back. New spark plugs, codes came back. New coil rail, codes came back. Replaced upstream oxy sensors, codes came back Cleaned throttle body and IAC looks new and moves, codes came back. Rough idle continues, going through 1/2 tank fuel in 50 miles. No smoke. Took to Firestone diagnostics, can't figure it out. Going back on Tuesday, July 25th.

[@courtneywomack414]

Did you ever get an answer? I’m having the same issue

[@jat-justamaturetech-philpj8285]

@@courtneywomack414 No! Not yet. Firestone told me to replace the TPS and use Mopar parts. I've been using after market parts. Waiting on a quote from them to put in a Morpar TPS, but I'm thinking, it all started from the cheap Chinese injectors I put in and might have them install the Chrysler OEM one's? Expecting a callback, and going to ask a quote for that. Probably gonna cost me $800? I have no cash, but, I have their C.C. which will make it easier to make payments. What brand of parts have you been using? I'll let you know if this solves my problem.

[@TB12DAGOAT]

Never thought about changing your catalytic converters

[@jat-justamaturetech-philpj8285]

@@TB12DAGOAT It was replaced about 2 year's ago, but I was thinking, maybe since my Jeep was running rich for about 6 weeks, may have clogged them? But I did replace all 4 O2 sensors. Thinking maybe time for Seafoam??? Update: I replaced the injectors with Chrysler OEM, and the Codes stopped, but still idling rough cold. TPS, MAP, IAC, Coil and plugs are new. Need to check plugs, may have gotten foiled, but don't think so in that short of time.

[@scottsprowl7484]

Maf sensor and or Map??

[@user-hr5dc4ly3q]

I used AF sensor from china but code still in the scanner

[@pamelaparrish4199]

I replaced both O2 sensors in my 1998 buick century li.ited. now the anti brake light and service engine soon light stays on plus the car cuts off while driving it. What's wrong?

[@Intense_hits185]

i recently replaced my o2 sensors 4 off them on my 2015 Chevy silverado but check engine light still on can i get some help on findig the problem

[@MNGZteam]

Did you fix the issue? I have the same issue. Had the P0420 code changed both cats, changed all 4 C02. Code for bad 02s came on the next day.

[@capzbaaan291]

I got a 2013 chevy equinox with a p2097 code was getting a sluggish acceleration to hesitation when accelerating.

[@dillon6320]

Same. Did you ever figure this out?

[@capzbaaan291]

@@dillon6320 was both O2 sensors but you have to recalibrate them aswell

[@TimeLapseCarGuyBruno]

can you do a video on p2237 codes thanks

[@williejae12]

Great video

[@kevinblount4596]

could an air intake leak be a cause for the code to return?

[@guanedits6349]

Yesss i had a huge hole in my throttle body air intake rubber.

[@Thibwe_dlo]

I got an EVAP/vaccum code at the same time as a bank 1 sensor 1. Havent found anything to fix it yet

[@markdavis8586]

Let the code sit. Don’t reset. Drive it as you normally would. It’ll clear on its own after a couple days of normal driving.

[@Thibwe_dlo]

@@markdavis8586 its been a about 2 months

[@seanhoward8025]

Here's a possibility...FCA issued a TSB to REPROGRAM the PCM back in 2008. The TSB is #18-011-08. This is for a false P0139 code being flashed intermittently. This will cause you to FAIL YOUR SMOG INSPECTION!!!

[@taemozzyarchie7035]

Changed all o2 sensors codes kum back Chang maf sensor as well code came back

[@rafaelsouzapedrosa]

hey guys how to code this oxygen sensor after the replacement ? i heard i need to turn off the battery but i'm not sure about that 😕

[@HVAC_Mechanic]

Most use a scan tool to clear the code and see if it returns. Often, a battery cable can also be removed, but this will also reset other things, such as the radio.

[@rafaelsouzapedrosa]

@@HVAC_MechanicI bought the sensor after the catalytic converter from BOSCH but the one before it I bought from another brand, would that be the reason I still have an error code on the sensor before the catalytic converter ?

[@rafaelsouzapedrosa]

@@HVAC_Mechanici already orded a new one from BOSCH as well, i'm waiting for the delivery.

[@pjdrcbashing6258]

Hi I have a weird one for you I have been pulling my hair out about this one and I'm not too sure where to go next besides changing my PCM but one day I got a code bad O2 sensor in my 05 Dodge Stratus 2.4 L dual overhead cam long story short I replaced the O2 sensors both upstream and downstream I cleared the codes started my car and the code came right back but came back as a low voltage for the O2 sensors so I've inspected all the wires and everything everything looks good the weird thing is if I unplugged the O2 sensors and clear the code the light stays off for about 30 miles and then it comes back as a high-voltage code but how is that if they are unplugged have you ever ran into this issue before just curious?

[@HVAC_Mechanic]

It is hard to say, but a failed PCM is fairly rare. Wiring issues can be a pain and often hard to find. I would check for any exhaust leaks or a clogged catalytic converter. Many techs would swap out the sensors again with Denso sensors.

[@pjdrcbashing6258]

@HVAC_Mechanic well my cat is hollowed out and I had a o2 code after I did that and had to install a restriction adapter to the downstream and the light was off for years until about a month ago the o2 code came back and my upstream o2 was melted so I replaced both upstream and downstream with the adapter on the downstream still plugged them in cleared the codes and as soon as I started it there were codes for low voltage on both o2 sensors tried to clear the codes again and same thing but with them unplugged I drove the car for 30 miles or more without the engine light coming on but when it did come on finally with the o2's unplugged it said that I had a high voltage reading from the O2 sensors which I thought was very odd considering they were unplugged the wiring and everything looks intact I can't really find any breaks or rubbing marks on any of the wiring is it possible that I could have a relay doing this to me

[@pjdrcbashing6258]

Hi I'm just curious do you know the voltage output from the O2 plug on the harness I'm getting 829 volts on my multimeter but I'm saying that I should have 12 volts there

[@ericgrajeda2671]

Can you pass a smog test for DMV with engine check light on?

[@crazyjavi1]

I cleared all codes my only code coming back is 135

[@crazyjavi1]

I replaced with a Bosch should I have done a denso?