P0420 Error Code Explained - Catalyst System Efficiency Below Threshold

The FIXD wireless OBD2 scanner and free app for iPhone and Android translates your check engine light into plain English so you can rest easy. In this video, we explain what OBD2 code P0420 means and possible causes.
P0420 means that the catalytic converter is not functioning efficiently in Bank 1, therefore increasing the output of harmful pollutants by the vehicle. The function of the catalytic converter is to break down harmful pollutants that are created by your vehicle during the combustion cycle and convert them into less harmful gases.
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0:00 P0420 - Catalyst System Efficiency Below Threshold
0:10 P0420 is caused by the Catalytic Converter not functioning efficiently in Bank 1
0:28 What is the Catalytic Converter?
1:11 Top 3 causes of P0420
1:26 Visit our blog to learn more about P0420
1:32 Happy Driving!
#FIXD #P0420 #checkenginelight

[@colleencunningham9063]

Informative and entertaining! thank ya

[@fixdapp]

Colleen, thank you for your feedback! We are glad you learned without being bored!

[@thatguythatmann3972]

​@@fixdapp

[@janalberti5567]

This video literally said nothing. Thank you

[@Fayis1341]

Just for views 😂

[@oyesimon8112]

It was self explanatory, if you wanted something more than go to a so called mechanic to tell you bullshit bcuz that's what most mechanic's are it's about the money and not helpful

[@Overcharge1]

Hilariously useless

[@Jester420JustinGaming]

Try turning up the volume!

[@TOSHADORTCH]

😂

[@aquaintsound]

Thank you so much. I now feel more confident talking to my mechanic about this!

[@b01ngb01ng44]

How did this channel instantly reduce my anxiety lol

[@louismaldonado8640]

This FIXD is the best investment I have ever made. It'll keep mechanics honest.

[@TomasRosado7]

Got this code while I was geeked off the zaza smh

[@allenavalos1193]

same bro

[@estebencampos146]

Lmao nah got this after cutting the muffler🤣💀I’m jus waiting for my 2 valve to come in cuz it’s gon open nd close manually

[@travisculpepper2091]

Lmmfao!!

[@chizuamajaegbu5230]

Same

[@LottoI95]

Damn two years later and this is still happening

[@LinkSquish]

When that dude said "ok good, what's the problem" It opened my "ok Google" thing on my phone. I played it back several times & it opened it every time. LOL

[@jamesn1008]

Hilarious!😂

[@rachidsabri5787]

Or it could be bad or disconnected vacuum switch valve

[@AndrexT]

I have this on my FIXD sensor at the moment. I have cleared it three times. I am going to try an in-fuel catalytic converter cleaner. I love the FIXD Sensor and the App.

[@fixdapp]

Thank you so much for the kind words and for using FIXD, Andrew! We appreciate your feedback. Hoping for a quick, affordable remedy to your P0420 code! 🤞

[@yvettepretty]

I used the oxicleaner it cleared the light for about 2 months so I bought another bottle it cleared then came back on. Good luck.

[@AndrexT]

@@yvettepretty The cat cleaner seems to have worked on mine.

[@YasirAli-nx5tw]

@@yvettepretty I have Toyota Prius 2016 new shape the code is catalyst system efficiency below threshold bank 1 How can we fix this please

[@ticketbabe]

Video was fine, did explain the basic issue enough to point in the right direction & did relieve anxiety for driving home from a vaca with that dang engine light on. Mostly, it became a venue for informative comments, which were great. Thanks FIXD & y'all from GrannieAnnie

[@fixdapp]

Happy to help!

[@jason3109]

For Ford focus mk3 first try the upstream o2 sensor as that will cause this code too

[@brendansweeney9719]

If you have a plastic air intake it might be cracked or ya might need to replace the intake valve. The intake valve might be cracked too.

[@fixdapp]

Great point, Brendan! Thank you!

[@rholt7448]

One must understand where this code comes from. Most see a 420 code and think they need a cat everytime. This code come from the down stream 02 sensor. The upstream 02 sensor is there to monitor fuel trim and the downstream is there to monitor the cat.

[@DOOMZDAY34]

Absolutely correct 👍

[@NORCALPYRO_]

What if i replaced both o2 sensors then the code came back 3 weeks later??

[@neoeyebeleave]

The code can be from different areas besides the down stream O2 sensor you know. High coolant usage can be a factor. High engine oil usage can be a factor. Engine misfires can be a factor. Etc. If it were just the down stream (rear) O2 sensor then that would be an easy $50 fix in a day.

[@derek4844]

@@neoeyebeleave agreed many just think it's a sensor without understanding of they are burning chemicals the cat isn't designed to scrub you test your cats with a thermometer before you pull the sensor.

[@Holly24tm]

What should I ask the mechanic to check? I have an inspection on Monday. My car is very old and rusted but runs so super well. Thanks for this info!

[@jesusaleman3620]

I recommend buying Catacleaner Before spending $200-1k , drive it around for about 15-20 mins or longer , return to where you were working on it. Disconnect the neutral from the battery to Reset the system , you DONT have to but it’ll take the check engine light off Sooner than just driving and letting it go by it’s self (could take up to a week) to simply turn off.

[@fixdapp]

Thanks for spreading the knowledge!

[@AndrexT]

If you disconnect the battery, don't forget you have to know the security code for the radio and you also have to know the security system reset or re-learn procedure. I don't suggest breaking the power to the ECM, BCM or any other management modules unless absolutely necessary.

[@NoahPARK82]

Hi there just want to know which brand Catacleaner is most effective thanks?

[@AndrexT]

@@NoahPARK82 Try Duralube Severe Catalytic Converter. I just posted and added a link to it but it vanished. Also try Scotty Kilmer YT channel and search.

[@johnbooker6524]

@@NoahPARK82 it's in a grey bottle. It's call catyclean. About 34 bucks a bottle

[@melissaburgess2753]

If it is a faulty O2 sensor shouldn't it bring up one of the sensor codes? I've previously had 2 brand new different O2 sensors installed in my 2003 Hyundai Elantra GLS & had a new catalytic converter installed.

[@meshackmisho5965]

what advise can you give to someone who completely removed the cat and get the error code

[@Jmata11]

Thanks

[@alfredohernandez636]

Thanks for the help I fix my truck

[@fixdapp]

Awesome to hear, Alfredo! So glad your truck is back in tip top shape. Happy and safe driving!

[@shiddy.]

what might cause this code on a 2005 accord 2.4 with a converter that's only 5000 miles old? converter was stolen a few months ago and was replaced with a brand new one ... code just popped today when it was really freezing out while it was warming up and the code is persistent and won't reset thanks

[@MrGiggsy90]

Hi and thanks for your informative video. So as i understand it is not dangerous to continue driving the car as usuall when we have this code. My catalysator has been stolen for a year ago, with the help of the insurance company i got a new one instead (original one as they said), now unfortunately i got the engine light on and detected code p0420 with my error code reader. I don't feel any problem with the car so i have just removed the warning with the help of my error code reader and it didn't reoccur yeat. Do you have any opinions/syggestions about that? Best regards/ prius driver from Sweden :)

[@MrTimedd]

This video is based off other videos only. The most generic information to get views. #1 P0420 is a *Generic* DTC( diagnostic trouble code) for emissions issues. This simply means your rich. The air fuel/mixture can be thrown of by many things. The number 1 causes for this is excessive *unburned* fuel. To much fuel for the catalytic converter to *burn*. Your 02 sensors are self explanatory. They monitor O2 (oxygen) levels which change depending how efficiently the engine is burning the computer calculated air/fuel mixture, BEFORE it even reaches the catalytic converter or exhaust. O2 sensors tell us the level of oxygen in the exhaust, indirectly via generation of voltage when oxygen passes through their electronic element. This being said, how does your car not burn fuel? A misfire causes rich fuel mixture to go through the cylenders without being burned...remember that trouble code we found before? P(powertrain) 0420(0400 series, emitions) (0020 exact sensors which detect a fault in the system) A dying coil pack can create misfires at high RPM and create a complete series of unburned fuel strokes to trip the O2 sensor. The cars main ECU(electronic control unit) that manages the cars Engine performance, (varies from manufacturer (pcm or 10 other acronyms) simply knows this information for emissions purpose. Some cars use 02 sensors to detect a misfire. Some don't. In face there are several ways. The whole point is. Many conditions could cause a misfire and cause other conditions which create a rich or lean condition. Leaking fuel injectors can cause this too. These electronic systems never tell the technician what the problem is. They only give us clues as to why the engine is not running at peak efficiency of 14.72 parts of air(baro metric pressure aka, bar 1) to 1 part of fuel. KZbin is one of the worst places for information because of videos like this. Suuuuure take your care to a mechanic who claims they are up to par with information like this and have been educated, (experience means nothing if you've done it wrong and just made people believe you know what you are doing) yet they rip you off with $2000 bill and you still have the original problem. The check engine light might go off for a bit. But it's the unburned fuel from the engine which sets this code.

[@MrTimedd]

@Nintendo Challenger X If you want answers. I'm available to give information.

[@whitelotusbodyworks]

@@MrTimedd Can you tell me what the best option for fixing this code is? My friend replaced my MAF sensor, and both O2 sensors and I still have the code. Tomorrow we are going to try soaking the CAT in Purple Power and/or water and laundry detergent. Is there any other option other than getting a new CAT?

[@MrTimedd]

@@whitelotusbodyworks You can look for vacuum leaks in the exhaust, which add a bunch of unexpected air to the system, before the exhaust reaches the Catalytic converters. Remember the code gets generated by the computer, (ECU, PCM etc...) Which only sees a certain trend based on what the sensors give it. If the sensors are tricked via the extra unmetered air in the exhaust, it's one way to make false codes. Did your friend be hit a tree branch? Or Have a new muffler put on, creating new back pressure? You need a scan too which reads legitimate "live Data Stream" here you can read voltage outputs from the O2 sensors and short term and long term fuel trim to tell if the engine is at proper air/fuel efficiency. If you could make a video no I'd be curious to see what's going on. Id really like to see if the cleaning works. There are other situations too. But as for cleaning catalytic converters. You need to fix what caused your cat to supposedly need cleaning in the first place, did the check engine light flash while driving? If that happens, it's a universal sign that tells the driver to stop the engine as the cat is to hot...To much raw fuel from a misfire, sometimes ignites inside and this flashing CEL, is the warning... Fire hazard. Any method assumes you do have a cat issue, so if you know the engine is clean(no gunk to fly into the cat) you could try one thing before pulling it off and using purple power. I recently bought and tried(bare with me) laquer thinner(yes the cleaner) to use in the fuel. 1 gallon to 10 gallons of fuel. I tried this as I've been having the same codes as you. In Truth I found better performance from the cats, but only initially in my testing. This only works if the catalytic converter isn't Burt to the point that it crumbles and clogs. Mine got fowled by fuel actually, so cleaning helped. But the original engine issue needs fixing to make sure I don't kill the cats again. I was testing this method as in automotive school, they say cat cleaning doesn't work 100% you simply get lucky. The link is to an example. kzbin.info/www/bejne/rKq5n5t5frJ3pNk kzbin.info/www/bejne/pnPGfXybgM-SaZo

[@whitelotusbodyworks]

@@MrTimedd Ok thanks! My buddy already took off the CAT and we're letting it soak. I will let you know how it goes.

[@engrprincetonykingstonnwac6044]

What happened next ​@@whitelotusbodyworks

[@2bd-bes]

What about the fix on P052B on 2013 BMW 528XI? PLEASE help

[@robertrobbins5456]

What if you have "Flow thru Catalytic converters? How do you get rid of the codes? I have P0420 and P0430.

[@Tommy2Txmes]

So would this be a common code to come up if my car is straight piped?

[@lloidpadilla427]

I removed my downpipe catalythic and put straight pipe can I clear the code somehow

[@Newyork535]

Nice, short .

[@ibarramurda]

I just got a 2014 Chevy Cruze two week ago and this code came up when I plugged in my Obd 😤

[@RealTamC]

What if sensors and catalytic convertor have all been replaced and the code still shows up.

[@mydreams8562]

Does that mean it's failed?

[@DesignerBrandon]

I got a P0420 code and couldn’t pass emissions. Dealer wanted $4k to replace the catalytic converter. I got some CataClean for $26. After about 100 miles CEL disappeared. I passed emissions later that day.

[@WhateverIWILLtoBe]

I want the 2 mins of my life back.

[@neoeyebeleave]

Me, too.

[@jdmcarboy64]

I got this code today and laughed because I’m long tube headers with full straight pipe 😂

[@jessv221]

And he said dont be 1 of those guys lol😂😂😂😂

[@avianavazquez]

I have a resonator, but no cat and got this code 😂

[@neoeyebeleave]

Pretty much never get any exhaust delete or straight piping work done if the "Service Engine Soon" light is on. It'll be permanent. Just fix the problem entirely first.

[@SaxHottie05]

I replaced my cat and am getting this code. So it could be a bad o2 sensor?

[@themusiclab2621]

The pot code lol

[@yrlovemusickh3948]

Hello sir I want you create videos about codes go on

[@Nerf1925]

Is all of the editing from this video theexact same as in the video for p0430 ?

[@Theonlytahboi]

How do you fix it tho

[@MyName-bq7vx]

Oh my mistake, I was under the ridiculous impression that a channel with the word “Fix” in its handle would, um I don’t know, fix it. You’d think someone with an obd scanner would have the sense to find out what it means. They watch videos to see how to solve this problem that present as some esoteric mystery. I’d call this video a miss if you we’re actually swinging for the fences. Gold stars go to effort but we got a lovely participant ribbon for you

[@dadosmtherealones7814]

Will never forget that code lol 420 yeeeppp. Thanks for this video tho. Very helpful

[@brianholder94]

Which part is BK 1

[@Gandalf17]

i only get this code during winter. When winter is over so is the code.

[@sammagambo9734]

Damn, I didn't know that Mason Mount repairs cars as well.😂

[@3fiftyone710]

Does it smoke when one of those is bad ?

[@eg6190]

a bit late reply, to my knowledge if you see black smoke and have this error code its 99% that cat has went out

[@THEashbeck]

Why this music in the background?

[@godovermoney1124]

How about if you just say piss on it & keep on trucking? No emission test required here

[@sgkdnay]

Had the manifold replaced, the catalytic (2 of them, upper and lower) replaced, muffler replaced, sensor replaced and STILL gives P0420 :(

[@nicolasrenderos2967]

x2

[@sunduq]

Thanks for the video, but the musical background is noisy and disruptive.

[@kevstamc3676]

I don't remember asking youtube what a cat converter is and how it works..I want to know what the code is and how to get rid of it -.-

[@franciscorobles7663]

Can this code mess up the car ?

[@deco.7798]

no shit, and probs the earth too

[@shinobitatsujin1136]

You made no mention of actually cleaning the sensors, and cat. which you can do for 20 bucks and 80% of the time it corrects the issue. Don't tell me you've never heard of CATACLEAN?

[@jerryzpro]

I tried mixing higher octane gas .. car was running better but now this 🧐

[@RPMusicInc]

Green screen + googling car codes+ highlight myself in thumbnail = profits???

[@fgrimm3]

how much would a new catalytic converter cost?

[@Shindaroo]

It depends on your car. Im bout to go have mine replaced on a 2008 chevy malibu for 525$

[@ShakaBroski]

$1,153.28 each for my 2009 Range Rover. I really want to try replacing the oxygen sensors first

[@elmecanico4943]

@@ShakaBroski How about replacing the whole car for a bicycle?

[@pro-impulse2831]

maddybeams bro, they don’t cost that each 💀

[@zl1camaro100]

@@pro-impulse2831 the mechanic scamming her💀

[@calvinperry1]

This video meant nothing I drive a duramax diesel so I don't have catalytic converters. Not sure why the code would come up on my truck

[@alanzorumble835]

So that means the o2 sensor can make the car burn more gas

[@kdeh21803]

Brand new CAT and all new 02 sensors and still a 420 code..... LTFT and STFT are normal....no vacuum leaks anywhere, new coolant temp sensor, and engine had just been rebuilt......code still comes on.... frustrating me to death

[@fixdapp]

What kind of vehicle are we looking at? Was the catalyst replaced with an OE part, what is the cell count for the new Catalyst? Many times an aftermarket Catalytic converter may be cheaper but will not work as well. If the purchased catalytic converter was a weld in part be sure it was put where the factory one was installed. It has to be in the factory location or close to it so it can get hot enough to work properly. You said the engine has been rebuilt, be sure the ring seal is ok with the new engine. If there is excessive blow by this could result in the catalyst being coated with oil vapor and not being able to reach the operating temp required for an effective catalyst. You can look at the front and rear 02 sensor operation also. The front O2 will be constantly adjusting from rich to lean. the rear 02 should be a fairly steady line if the catalyst is working properly. Be sure you do not have any exhaust leaks pre cat/pre o2. If the rear 02 is matching the front then the catalyst is not working how it should.

[@g.s.7383]

fuel pump - replace it, sometimes MAF Goes bad as well. But my take it the fuel pump.

[@kdeh21803]

@@g.s.7383 Fuel Pressure checked at the rail is within specs...... I have dealt with the 420 code before and it can be quite frustrating.

[@kdeh21803]

@@fixdapp direct fit catalytic converter for my supplier, brand new O2 sensors, and the engine was rebuilt buy a guy who builds engines for racing.

[@prolly2stoned420]

How about 0706? 😱

[@StarrSun]

Tease post

[@vtracing1765]

This is not all true.. p420 does not shoot out black smoke

[@samnyiri2135]

I have this code on my B7 A4... but I'm running test pipes... with the o2 still attached and functioning. Just came out of nowhere too... any ideas?

[@fixdapp]

The rear 02 sensor acts as a monitor for the catalyst. When the vehicle is driving and reaches full operating temp, the ecm will run a readiness test to verify all is well with the catalyst system. The purpose of the 02 sensor is read how much unburned oxygen is in the exhaust as it exits the engine. Monitoring oxygen levels in the exhaust is a way of gauging the fuel mixture, or fuel trims. It tells the computer if the fuel mixture is burning rich (less oxygen) or lean (more oxygen).In the case of test pipes, the catalyst is deleted therfore the sensor will read as if the catalyst is not working properly, when it fact is not there. You can clear the light but it will come back on eventually. Many times vehicles with test pipes, big turbos etc, will have a tune that works with the test pipe to keep the light off in states where there are not emissions.

[@jjjda7441]

Just read the temperature of the catalytic converter at idle with "hot" engine. I mean if the converter works properly, the rear side is warmer than the front side. 50 degrees Celsius more

[@ImA1032]

What I want to know is who's the comedian that decided to make an exhaust (i.e. smoke) code 420? 🤔🤔🤣🤣

[@edkonvang]

more importantly make sure you subscribe...ha!

[@ChildOfTheAlmightyGod1974]

Manifold exhaust leak

[@jimglassford9967]

The attempt at levity is just a distraction. AS for the actual content, he is basically saying if the check engine light is on, there is something wrong. No real detail past that.

[@HaddaClu]

This code came just about an hour after my vehicle pass it's state inspection so I doubt its the cat.....

[@user-sg2yt6nc1z]

I just got a new cat and oxygen sensors and I patched up all exaust leaks and I'm still getting the p0420

[@fixdapp]

P0420 fault can be tricky sometimes. The fault is stating that the catalyst is not working efficiently based off what the rear 02 sensor is reading. Many times the reason a catalyst fails is due to something else in the system that caused it to fail.There is an 02 sensor in front of the catalyst (pre cat) and an o2 sensor after the cat (post cat).The front oxygen sensor is the primary 02. The second (post cat) is the monitor. If there is an issue in the engine causing the car to run rich or lean the car will adjust to compensate for this issue trying to fix itself, and in so doing can cause a false reading indicating the catalyst is faulty when in fact there is another issue. Example: coolant temp sensor is faulty and telling the pcm that the car is very cold. This would cause the pcm to add more fuel which would result in a rich running condition. The rich running condition could add too much fuel to the catalyst causing it to not be able to heat up properly and reach the correct temp. This would cause the rear 02 to read as if the catalyst is failing when in reality it is because of too much fuel causing the catalyst to not work 100%. I would suggest looking at fuel trims, verifying 02 sensor operation/voltage and go from there.

[@stuartracing1]

I gutted my cats. and now I`m getting this po420 code...I have a hand held programmer and a tune from a shop...

[@fixdapp]

If your catalyst is gutted and the vehicle's ecu is still using the rear O2, which it will do unless coded out then you will get a p0420 fault. The job of the rear 02 sensor is to monitor the efficiency of the catalytic converter. I would suggest giving a call to said company you purchased the tune from and see what they do for your particular file. Without a specific file change this code will most likely come back. There are times when people have used O2 sensor spacers etc., however I would find out how your ecu tune is setup and go from there.

[@stuartracing1]

@@fixdapp I first deleted the rear cats years ago with no problems..Then a month ago or so, I gutted the front cats and reinstalled the front two 02 sensors after,installed two new perf mufflers..I got a P0430 code a while back but nothing since..I called my tuner guy and he said if it returned to let him know and he`ll readjust the tune..

[@trumpour12]

I learned that Anakin went to Tashi Station and got Power converters and I learned nothing about Catalytic Converters..

[@mendezfocus]

I appreciate the mechanical explanation very good I liked it a lot I just don't appreciate the lgbtq commercial in it please take it out

[@baseballfury7756]

Whoever fixes this code is a total party pooper

[@justinheiden3470]

Can I just do a cat delete

[@neoeyebeleave]

Still gotta fix the issue entirely first. Otherwise it's stuck on "Service Engine Soon" forever.

[@pwash474]

You didn’t solve the problem, you took 2 minutes to explain how a catalytic convert works. Lol

[@AgentAbel]

Customer states: "Just change the oil!" The check engine light:

[@ActionBastard88]

Time to spent like $200+ on a new cat

[@jbortega1178]

Could putting regular gasoline as apposed to the premium its suppose to lead to this? Just a friend asking for a wife so she don't get murdered

[@karymmassuh2798]

While I’m smoking weed this shit happened

[@jcnlala9461]

Thanks for nothing😂😂😂

[@danny-sz2on]

Fuck it straightpipe.

[@martinvalenzuela1040]

Why do people make videos that waste people’s time?

[@sairamgottipati1004]

How did you get these many subscribers. not at all useful vedio dude.

[@davidjsouth231]

Yep that’s my wife’s car. I’m just dreading tearing it apart

[@vell8807]

Bruh said a whole bunch of nothing

[@gmoney120199]

So the silly lil wife didn't want to listen to her husband?! She clearly didn't know mechanics but this video is supposed to show reality?! SHDH

[@ahotdj07]

He’s a cutie

[@totalannihilation9065]

Lost 1:37 of my life for this?

[@MilkCrate801]

be sure to keep our environment radical and clean my fellow game assassins

[@Edgar_Calderon]

Thank you for nothing

[@archiehitler5264]

Rubbish