The Trainer

#p0420 #p0430 #catalyticconvertercodes #badcat #autel #motoragetraining
The “Catalytic Converter Efficiency” codes, P0420 and P0430, are among the top 10 DTCs technicians face. And while the description might imply a failed converter, odds are the ultimate fault lies somewhere else.
Learn more in today’s episode of “The Trainer”!
Don't forget to check out our sponsor at www.Autel.com
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Due to factors beyond the control of Motor Age, it cannot guarantee against unauthorized modifications of this information or improper use of this information. Motor Age magazine (Endeavor Business Media) assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Motor Age recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of Motor Age, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage, or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not Motor Age magazine or its corporate parent, Endeavor Business Media.

[@bradpetersen92126]

After chasing my tail a number of times trying to troubleshoot a P0420/430 DTC, I would check the manufacture’s list of TSBs and see if there were any software/reflashes that might address the issue. Wasn’t unusual that new vehicles had very tight software constraints to get them certified and keep the EPA happy. After the vehicles amassed many miles through a myriad of conditions, updated programming via reflash gave the ECM a bit more elbow room to keep the MIL off. That “Silver Bullet” saved many of my customers the high cost of converter replacement. signed, One happily retired 35 year ASE Master Technician…

[@2nickles647]

Basic maintenance sure saved me alot of head aches over the years. My wife said. I love the way your truck idles so smoothly. I just smiled.

[@Maxy_Boy09]

I had p0420 code so I changed lambda sensor post-cat and all spark plugs and then after a week the enginge light disappeared ✅

[@jayway8612]

youre gay, no woman ever says that...unless she wears a strapon

[@familiacarrion7935]

This person is a 😢 very professional person, thank you for your advice.

[@LarsDennert]

Definitely first step is basic maintenance and spark plugs. Then track down all vacuum leaks. After that make sure o2 sensors are good and finally cats as the last resort.

[@mikeschlup5279]

Did all that on my 07 V8 4 runner...down to front exhaust manifolds and cats...

[@thejagmohan7121]

I got this code after changing spark plugs and ignition coils and driving about 50 miles or so. I've done the replacement twice already with no problem. No misfire codes just p0420 efficiency low bank 1. Any ideas?

[@LarsDennert]

@@thejagmohan7121 loose plug could cause it. You used the spec denso or ngk plug? If it wants platinum don't use iridium or vs versa. Some motors like the Toyota 3.4 are super sensitive due to the reverse polarity coils. Hard to know your situation based on the general post

[@justingrabowski8142]

@@thejagmohan7121did you scope the O2 sensors?

[@c.p.5741]

​@@justingrabowski8142what does that mean?

[@dakota51tpa2001]

All of these are great tips, but let me tell you my experience. I have a 2013 Nissan Altima S with the 2.5 4 cyl. For several months I was plagued with the P0420 code. My mechanic tried all the usual diagnostic techniques, checking o2 sensors, cleaning the catalytic converter, even going as far as gutting the rear catalytic converter to relieve a suspected blockage. The problem not only persisted, it got worse. Instead of coming on every 150 miles or so, the Check Engine light came back on every 50 miles. I have probably spent around $500 trying to get the stupid light to stay off. You know what finally solved the problem ? As per routine maintenance, I removed and cleaned (I have a K&N) my air filter. I cleaned and re-oiled it according to K&N's instructions and re-installed it. NO MORE CHECK ENGINE LIGHT. After all the hours and all the money needlessly spent, the solution was to clean my freakin' air filter ! Something so basic and elemental, I didn't even think of it. The lesson here ? Check the most basic, cheapest stuff first. You may think you have a special car with a problem so unique, no mechanic has ever seen it before. In all likelihood, its something simpler than you or your mechanic realize.

[@jeffflanagan2814]

Just a heads up if you use a K&N, keep your MAF clean.

[@borkganza9627]

EXACT SAME THING happened to my son on his G6. His mechanic told him some cars don’t like the K&N filter.

[@wazzabanzook5028]

don't use K&N filters , use oem

[@tonyisme4934]

Save the K&N for the dirt bikes. Use OEM air filters. I put original OEM air filter in my Lexus LS400 and now I'm getting better gas mileage. Switch to the OEM Air Filter and run a can of 44K Platinum by BG in a full gas tank. That got rid of my Check Engine light. My CATs have 278,000 miles on them. I always use 44K and it gets rid of my check engine light for quite a while. I use Chevron gas. My emissions test results way below the limit. Codes P0421 or P0420, OEM Denso O2 sensors.. Lexus tried to get me for $4000 for two CATs Ha Ha Ha Bozos

[@septimustyrannis321]

I had a similar problem. But it wasn’t just cleaning the Canon air filter it was also cleaning the mass airflow sensor. The thing that pisses me off is the three mechanics I took the car to when I was having these issues all they didn’t look at codes and replace parts. That’s what they are parts replacers. They have no clue how to diagnose anything on their own without a computer.

[@donaldappelhof2059]

The problem is finding someone that knows something.

[@FlyingV555]

Extremely true

[@rp6236]

The problem is finding someone who is willing to pay someone who knows. 😊

[@donaldappelhof2059]

@@rp6236 I would gladly pay someone to check out my truck that knows what they are doing. I want a guy that understands fuel trim’s and all this other high tech garbage. Last guy said 02 censer and that fixed nothing. I would also like someone who knows how to tweak the computer. I haven’t found anyone yet other than part changers. Hell I can do that! I did fix the track control problem. My tires looked good but I you really look closer one was separating. As soon as I pick up speed the one wheel would throw a code. New tires a it never set a code again.

[@podunkpennsylvania292]

Glad to see a video about Cats that is informative accurate and all around a good routine for diagnostics. Bravo.

[@joylitz2477]

experienced an interesting one in regards of this code P0420…it wasn’t my cat at all but rather it was the oil leak that spread under my car due to negligence oil changed my oil guy did…my Hyundai dealer discovered it and saved me $4K of cat repair costs…it was a breath of fresh air after I learned about it

[@JA-rn5qv]

Yup I've seen that happen. Some cars have oil filters located directly above (or close enough) to the upstream 02 sensor and that oil filter can be in a very restricted spot in which you don't have much of a choice but to make a mess when you remove it. When that happens it's very possible for oil to leak/splash/drip on to the 02 sensor and eventually work it's way through the threads and contaminate the sensor. I've seen this mentioned as a common issue in several car threads to the point that many car owners of that particular make/model started doing their own oil changes so as to not have to deal with the P0420 shortly after each oil change. This is also a perfect example of why it's so very incorrect to assume when a P0420 code pops up that it's the cat. The vast majority of times I've deal with that CEL code, I've been able to resolve it other ways. Only once was it a bad cat and that was within the warranty period (luckily) and it was also quite obvious that it was the cat because it sounded like a metal can full of pebbles sliding around under the car when coming to a stop or accelerating indicated a shattered catalyst. But every other time, it was not actually a dead cat and the resolution was usually relatively simple and a fraction of what it would have cost to replace the cat and/or sensors.

[@jludtxs]

What do you use to clean the oil off? Mine isn't leaking but there is a lot of oil all over that area.

[@joylitz2477]

@@jludtxs I didn’t clean it myself but I noticed when I brought it to my mechanic and told them about it…they air pressured hosed it underneath with some water and wherever the leak was coming too from the sides

[@keithburningbush6456]

I bet you're 2qt low of oil every oil change🧐

[@packrat9433]

@@keithburningbush6456 Can you elaborate on that? I'm a backyard but capable student. But I don't follow your tweak there. Are you saying they spilled a lot of oil? or something else? Just wanting to learn.

[@SwordFighterPKN]

Diagnosis like described is like watching the carpenters on this old house, it's how things should be done but rarely are.

[@billybarnes9208]

Got the code on my wife's car. They tried to sell me a converter. Then I realized it happened after daughter put gas in the car. So I checked the fuel cap problem solved didn't even have to replace cap. May God bless everyone!

[@MR..181]

Me too after paying for a new not quality converter..at 102,000 miles..from q government recommended repair shop ..

[@Cutekittee]

I think this is what's going on with my car. Either that or because I got gas from a place I don't normally go to. Came on the next day after I got gas and it seems like my gas cap isn't getting vacuum sealed when I put it on

[@dwightcarlson7136]

Excellent video. Just the tip about the shop vac to find leaks was worth the watch.👍

[@bze06fishinbwai63]

So by doing that, just spray the soup/water on the hoses and hopefully see a leak?

[@DeElBee]

@@bze06fishinbwai63 Yes, on all the exhaust pipes, and then hoses in the engine compartment.

[@sollykhan2385]

Another splendid tutorial, Sir i salute you for all the great effort you put into these awesome videos, Thank you and please continue

[@allimkhan7540]

Excellent Video this guy knows about cars . He explained everything very well !!!!!!!

[@ambers4483]

Thank you for this video, this is exactly what I was looking for!

[@Swimbait_addiction]

I just got my 1st Autel today. MK808BT. So far I'm loving it. Just changed a bad ABS module and was able to flash it and fix my abs lights in my town and country 3.8. This 0420 code is all I have left and both 02 sensors are new so I'll be checking out the converter. Awesome video. Thanks

[@andrewhigdon8346]

I think the point of the video is that just because a code is thrown for a certain component, that component itself might be the singular issue, having lived it’s long life, and time to be replaced, like spark plugs, ignition coils, batteries, brakes. But more often than not, by a large margin, the actual cause is because of another component which is malfunctioning and it’s symptom is causing a reaction in the component that is represented by that code. You could replace that component every month and still not fix the problem.

[@timtaylor9339]

With direct injection engines it can be the injectors. The code is often accompanied with a cylinder miss code.

[@nexus2lexus]

Just a heads up, injectors on a direct injection engine are under such tremendous pressure compared to port injection. Injector issues on DI engines can actually cause compression issues. If DI injectors are ever removed for any reason, they must be replaced with a new injector to prevent compression issues.

[@123456789shaikh]

Great explanation covers everything Thanks for helping

[@mikecarter694]

I had this code on my Chevy Cruze LTZ. A fresh set or plugs and a new coil pack solved my issue. 170k miles. It was due for a tube up. $200.00 we’ll spent.

[@LOLONO666]

did you notice a black smoke

[@pedrovillalobos2037]

@@LOLONO666 Only when smoking pot, I guess, LOL

[@royergonzalez4361]

What in the world is a tube up ?? Lol

[@royergonzalez4361]

Do u mean tune up ??

[@lozanospain1]

Cristal clear,very useful info,as you say sometimes a cat issue is tricky to confirm .. best video and explanation about cat issues i see... Keep it up. Greetings from Spain 👌✔️

[@HipHopBeatSource]

Very helpful video. Thank you!

[@artiemejia3695]

This was VERY informative. Thank you.

[@VelvetteNoir]

Can't tell you how much I appreciate you posting this. Your presentation is professional, and instructions thorough and detailed. Unlike other videos with "quick fixes" that are on par with slapping a band-aid on a gunshot wound, you covered what's most important: the root cause(s). I was able to determine the state of my cat (spoiler: it's failed 😅) before my lunch break was finished. Thank you again for a fantastic break down. I look forward to your future content!

[@LourdesS]

Great video and took my anxiety down a notch!

[@Stonerolog1st]

A P0420 just mean the car has developed a smoking habit

[@dianagirdharry7635]

Yeah! mine did 🤣

[@mstchiefa7892]

This was very thorough

[@terrellscaife2411]

Thank you I learned a lot today while watching this video thank you

[@richborzea4589]

I must get that Autel thermal imaging cameras. Thanks for the diagnostic tips!

[@buzzbuzz6834]

🤣😂🤣

[@doctormoto8770]

Great video sir and thank you for your help! 👍

[@bywayz]

This is a logical troubleshooting process ... and one I cannot see the typical independent or dealer mechanic spending time on. Two dealership techs independent of each other relied solely on DTC readers -- and incorrectly diagnosed the need to replace both of my 4Runner's cats and related sensors due to severe loss of power. Neither fixed the problem. An independent could not identify the source of the problem, either. Finally, my old-school pre-ECU carbureted background whispred "fuel pump," and I insisted under emergency circumstances that it be replaced even though the dealer tech was very leery. I was right ... but also several thousand dollars lighter in the bank account. Apparently, a bad fuel pump will not send adequate fuel, causing lean codes that seem to DTC readers to be cat-related. The lesson is that typical techs either cannot or will not do the kind of research outlined in this valuable video.

[@jeffflanagan2814]

Their is no possible way that I know of for a lean code to be determined as a cat failure. Whoever you took it too either did not know what they were doing or knew exactly what they were doing! Did you receive your old cat back?

[@bywayz]

@@jeffflanagan2814 No, I did not. Didn't even think to ask. It was a bad situation all-round, but it is fixed now. I the end, I have two new cats with sensors, all new oil-control valves (another misdiagnosis, but they were indeed in poor shape), and a new fuel pump. All this at less than 160k miles, not what one expects with a 4Runner.

[@jkkennedy8919]

@@jeffflanagan2814 exactly

[@stillwaters6198]

Did you recover any money from the mechanic?

[@elijuh3]

@@stillwaters6198nope but I bet that mechanic sold his old cats to make some $.

[@mikeoneill7360]

Excellent presentation…..

[@damonhighley5020]

I took out the o2 sensor, installed an anti-fowler and reinstalled the sensor. Haven't had an issue for years. LOL.

[@Jordanjuggin]

does this affect economy or performance?

[@jessejames96]

@@Jordanjuggin shouldn't affect either

[@serchizm]

What’s an anti fowler please?

[@kimokahikolekalihi]

​@@serchizmit is a threaded pipe that threads into the O2 sensor bung and the sensor is threaded into the end of the pipe. This puts the sensor outside of the exhaust stream helping to have a steady O2 reading on the secondary O2 sensor and avoid throwing a code. On some cars this works and some it won't.

[@thejourneymen7722]

My PO 420 code came on due to a Fram extra guard air filter that I had just replaced went back with original equipment Motorcraft air filter in PO 420 code went away, not saying that there’s not some underlying issue but that’s what removed the code on my 2018 Ford F150, 2.7 L.

[@ripptydevibes2581]

In the North East we most commonly see faulty converters. Exhaust leaks will show up in the fuel trim data, if theyre affecting the converter. Exhaust leaks are audible, and traceable in fuel trim data. 95% of the time, its a bad converter BUT the first step is to replace the rear o2 sensor, then the cat if code comes back.

[@Mike_Hog_A_Nator]

I have an 02' Blazer zr2 4.3ltr. Got a new Cat, Rotor, Coil, ECU, Wires, Plugs, etc. My Check engine light came on & got the 0420 code. Exhaust is new also. It showed Bank 1 below temp. threshold. I changed bank 1 02 Sensor & same code came back. I do have another 02 Sensor located on Bank 1 Sensor #2, the 1 just before the new Cat. I'm installing a new 02 Sensor there today. No leaks, etc. Everything I had installed has less than 400 miles. The Cat is a high flow, Flowmaster Cat & the Mechanic Shop said it wouldn't throw a code. Zero power issues. The Truck is running great even with the light on.. I cant even feel it idling at a red light with the AC on!

[@MotorAgeMagazine]

Unfortunately, that might not be true about the new cat throwing a code. One reason why a few states require cats certified by CARB. What is the code number that you are dealing with?

[@ghahandi]

Have an '04 4Runner V6 4.0L. Had 420-430 and 206; cylinder6 misfire. The #6 plug looked oily- Checked compression 175 psi. No loss of coolant or oil. Good compression. Installed new valve cover gasket set. No more 206 code . Still had 420-430- ran a couple of bottles of cat cleaner & one gallon of lacquer thinner through the engine, per "Scotty". No help there. The 4Runner runs like a banshee. Very quick response. No sluggishness. No foul smoke from the exhaust. No issues with exhaust leaks or vacuum leaks. Changed both downstream sensors & added spacers to the downstream o2 sensors. No more 420-430. Passed smog, then I removed the spacers. Ran good for about 2 weeks before the 420&430 reappeared. I will reinstall o2 spacers (also known as spark plug anti-fouler); you can buy o2 spacers on line with out having to buy two 2 spark plug anti-foulers per o2 sensor, then having to drill the outboard fouler to accommodate the o2 sensor. Just buy the spacers on line. they are cheap & install easily. They come from China, so may take3-4 weeks to receive, but they can work. no guarantee, but cheap enough fix & often times does work. If the problem does not go away after I reinstall the spacers, I will buy a pair of new after market cats- For the 4Runner-they are multiple listings on eBay & Amazon. Any reluctance of the seller to ship restricted state (like mine: CA) I tell them it's for my ranch truck, not registered. They will ship it. They want the business~😁😁 There are YT vids on the spacer install and the anti-fouler method. search them out. Some spacers actually have a mini-cat screen in them. Again-they are cheap.

[@MotorAgeMagazine]

Cheap - yes. But it isn’t a fix, its a bandaid.

[@jhill4071]

My take away. Over time it sure pays to live in a state that does'nt have the smog check inspection fraud.

[@JYAN2852]

Ugh dealing with this exact problem now. Damn politicians

[@arthursmith1732]

I’ve been ase cert tech and service manager over 40 years and the only fraud l’ve seen is poor diagnostics and ignorant owners. Most cars and trucks thru the shops l’ve worked have hundreds of thousands of miles with original converters working as designed. Not a perfect system, but the best we have if we want to continue burning fossil fuels. Basic maintenance consistently performed is enough to keep most issues at bay. There will always be exceptions and poor designs and manufacturers.

[@JYAN2852]

@@arthursmith1732 So my car is 17 yrs old with clost to 200k miles. The stock cats are no good they have lasted for as long as they could now throwing P0430 and P0431 trouble codes. I'm in California where it is illegal to install EPA cats. Plenty of those availalable but no retailer will sell nor ship EPA cats to Cal. Politicians will only allow approved CARB cats as replacements, none that exist in their database for my vehicle. I spoke with the state emissions rep they said my only option was to junk the car when there is nothing else wrong with it. Many others are going through same issue in my state. I don't see how this is caused by ignorant owners

[@daniellefunk8991]

@@JYAN2852 I knew you were in commiefornia when i saw your first comment! Im also in this ridiculous state and i have been going NUTS trying to get my damn van smogged! Ive scowered the internet looking for the right damn cats and when i finally find some, THEY ARE THOUSANDS OF DOLLARS!!! Thanks a lot gov newscum!! I hate this state cus of that commie bastard! Ive tried cataclean a few times and paint thinner too! Damn light keeps coming on at or before forty miles! Ive put TONS of money into this van and i will be damned if i am gonna scrap it!!

[@lozanospain1]

This is only possible in the U.S...in Europe you have to pass this test .. Hey look for the environment...and for our planet...hahaha 👍

[@gpweaver]

That is a brilliant way of troubleshooting exhaust leaks! Beats my way of crawling under the running car and running a bare hand around all sides of the pipe/joints trying to feel a leak...or waving a cigarette around looking for the smoke getting distorted (which, since I switched to e-cigs, is a lot trickier 😃)

[@tehagent1321]

Could probably take a big puff and see where the exhaled vapor goes maybe?

[@gpweaver]

@@tehagent1321 Yup, that's what I do now, but it's not a steady stream like a good ol' cancer stick gives ya.

[@A-tone-gk7pb]

Good video he an expert knows what he's talking about

[@Powerstroke98]

Helpful information! I have the Autel AL519 which told me I had an issue on Bank 2. I deleted the code after checking the front & rear temperatures, as the drivers side seemed to have a wider difference between the two (which I believe is bank 1) as I have 2 converters on my F150 pickup. Interestingly, it's been a week, and after having the initial code come up, it has stayed off, although I will test again today. Thus makes me wonder if it was a random code that popped up for some reason? Nonetheless, it's something I'll be keeping an eye on. Thanks for the video! Having 137K on the truck, I would imagine the converters 'may' be getting to the end of life, but I'll continue to watch for check engine lights. Fuel mileage hasn't really changed either.

[@Vibetribearth]

Thank you!

[@markkukowski3710]

As a "seasoned" auto tech, I have had trouble at times with the P0420/430 codes. Most of the time, it ended up being a bad cat convertor as you can watch the downstream O2 sensor switch as fast as the upstream: This almost always indicates the convertor is bad. I have found air/exhaust leaks to cause it, of course and I have found a similar test: You can use the evap "smoke" tester in the exhaust. This has saved me many times. Also, many aftermarket convertors are made cheaply and not as efficient as the correct factory unit. I've installed these and had the same code reappear. When I finally convince the customer to spring for a factory unit, the problem goes away - Just sayin

[@GrievenceCapitolist]

I just bought a smoke tester to hang from a branch in my shade tree . I know what I'm doing tomorrow . Thanks .

[@user-rk6ry2bv5e]

In my case had more voltage from altenator and make ECU to read false from O2 sensors the car has 240.000km or 148.800 miles , when fixed ( altenator ) P0420 code gone after some miles , without erase from ECU .

[@borntowin1017]

I love your videos very knowledgeable! Learn a lot from you sir! My name is TASHA from USA 🇺🇸. My check engine light reads that I need to replace ignition coil and spark plugs as well as a cylinder 4 misfire secondary DTCs, p0420 cat efficiency helper threshold bank 1 and 83-13 ECM/PCM relation failure. I have a Honda Accord 2009 LX. I’ve driven like this 7 years! Now I fear how much repair will cost. Why me? 😩

[@priestlygarments4004]

I love your videos very knowledgeable! Learn a lot from you sir! My name is TASHA from USA 🇺🇸. My check engine light reads P0304 a cylinder 4 misfire secondary DTCs, and P0420 cat efficiency helper threshold bank 1 and 83-13 ECM/PCM relation failure. I have a Honda Accord 2009 LX. I’ve driven like this 7 years! The Engine Light Has Been Solid For 7 Years. Should I be worried? And can I keep driving like this without risking my health?

[@striderwolf687]

We had this code and a mobile mechanic was able to use his professional scanner to show the two banks, upstream and downstream measures, etc. It was very helpful to see this info vs. guessing. We got an OEM cat, replaced only 1 cat of the 4 (thanks 4Runner), and no more code.

[@dayntubee]

YOUR EXPLANATION THE FAILURE OF A CATALYTIC CONVERTER AND WHAT CAUSED IT IS ON POINT AND EXCELLENCE! CHECK AND VERIFY!

[@Discretesignals]

Also look for factory TSBs. Could be software issue. Some aftermarket cats aren't loaded correctly which can lead to a comeback or cat monitor to fail.

[@dexaler9008]

I've read several comments and agree there are several different causes. But, for me, the code is for Bank 1. This means that the side of the engine with Cylinder 1 has an issue. Therefore, it does not seem like common components of the engine are at fault - such as a dirty air filter or MAF. It seems more likely that the issue is related to that side of the engine and it's combustion, oil, gas, adn exhaust components. Has anyone had an experience where the code specifies Bank 1 but it was not necessarily fixed by a component related to Bank 1?

[@YakanAutumn]

My car currently has this problem and I'm just trying to find what parts to fix before I get the cat.

[@bze06fishinbwai63]

@@YakanAutumn My car has the same, P0420 Catalyst system Efficiency Below Threshold Bank 1. I just saw a video that said to try the Catalyst sensor, so i just bought it and will put it on. Hopefully that will fix that damn ISSUE!!!

[@solidat1619]

@@bze06fishinbwai63 uppdate on How it went.

[@mervdat6813]

@@bze06fishinbwai63 did it work?

[@justguz1180]

@@bze06fishinbwai63 we need a update! 😂😭😭

[@TurboMountTV]

Cat cleaner removed the check engine light on my old lexus. But the VSC ON OFF lights still on (which go on in Toyotas when the check engine light goes on). Any ideas?

[@vinmarz]

Cataclean works for me everytime!!!

[@zanetracks6592]

Several years back I followed Scotty Kilmer's advice for a catalyst failure code. Added acetone to a low fuel tank and ran it. The code resolved and never came back.

[@jeffflanagan2814]

This is Gold!

[@catmontoya2075]

My 2018 Dodge Journey has the code and Drives sluggish…it always seemed to have since I got it new in 2019. I changed the nasty engine filter. Anyways, this video was helpful in understanding the mechanism of the CC and the code. So begins the “journey “…🤣

[@coryament]

Most likely the upstream sensors on a late model chrystler. Had it many times

[@ksajak]

What did it end up being?

[@JockeyCake]

Thank you very much Sir

[@michaelmartin2276]

Great video !

[@TheMorumotto]

An extraordinarily smart and kind gentleman, he explained the basics and specific things. My Charger's converter was sentenced by "professionals" in the dealership, but it turned my engine was running lean due to wrong calibrations. So, I got my PCM replaced and the P0430 code is gone and not coming back.

[@nicholastanton8404]

Damn right "the dreaded code". Very difficult to diagnose. Very frustrating.

[@johnhufnagel]

being a 00s chrylser guy (with several in my fleet), i'm very familiar with the O2 sensor outputs and their readings on my Autel MS 906Pro. However a friend of mine had the "dreaded" P0420 code pop up on her Honda. The software on the Autel doesn't report Honda's sensors (2013 Odyssey) in the same way, so I was struggling to help her diagnose, is it a bad cat or a sensor problem. Curiously, the MIL went out on its own, and the code was stored as permanent, but not active. In fact, I had to use EOBD to read both sensors, with the downstream in V and the upstream in mA. My educated guess is she has a bad upstream sensor, and not a bad cat. I came to that determination based on comparing the upstream data between both banks, and noted that bank 1 would occasionally be "smoother" than bank 2, instead of roughly tracking the same, and even once go completely flat line at 0 mA. I considered a possible wiring fault, but the fact the traces look like a sensor getting "lazy" or "falling asleep slowly" then suddenly "waking up", makes me lean towards a failing sensor rather than a wiring issue. The downstream sensors would also follow the upstreams in their reporting and graphing. Where would a DIY shade tree home owner mechanic go do to find more information about specific vehicles and their expected O2 sensor outputs and performance.

[@amandaeaton3919]

So it's an exhaust leak. That makes alot more sense. I knew there was a Crack, and my tailpipe dropped a bit this last week and now it's running like crap and throwing those codes. Thank God I was already ordering a muffler

[@AnnieAint]

I have a brand new catalytic converter put in October 2021 on a 2002 Toyota sienna and now I’m receiving the PO 420 code so I can’t pass emissions. I feel like a two-year-old catalytic converter should not be having this issue or is this too totally separate items? Thank you. Edit: I understand now.

[@daraprak6498]

Reason #197 why I love Texas, I drive a 91 bmw e30 325is and all I need is a safety inspection so no cat converter is needed to pass inspections 🥳🥳🙏

[@sunshinedayz2172]

Thank you Mr Trainer👍 Im a single woman trying to survive this code..my truck is a 1998 gmc 5.7 sierra truck 2 wh drive..

[@chasechevy8933]

Great, informative vid

[@bernarddrenzcampbell2757]

I got the check engine light with Po420 code but every time I drive 45min-1 hour on the highway the check engine light goes away for a day or two then come back on?

[@JasonSmith-utube]

If your mechanic is not a technician, tread softly. Now days most problems can be determined with a scan tool, oscilloscope, laptop, smoke machine, and fuel pressure guage. Never let a mechanic "try this" or he "thinks it's that". If they cannot explain what your problem is, why it's bad, how they determined or diagnosed the issue, or show you what /why a part needs to be changed. Do not let them work on your vehicle. Don't think we'll the O2 sensor didn't fix it, but it had 100k miles on it anyway it needed a new one. No! Most of the time you are trading a perfectly good working OEM very expensive part designed for your vehicle for an inferior aftermarket part. And it will not last as long, some ECMs will be further confused by the non OEM part and it will say it will work with your vehicle but it might not work very well or cause another problem. A reputable technician will only change the part or parts that fix the problem. Not charge you 5000 for shit you didn't need and keep your good working OEM parts and sell them on ebay or use them on another customers car and charge them for new shit. It's easy to tell who knows what they are talking about. Guys caked in grease, that don't use electronics 1st, are the wrong people to be talking to. Also the tech that works the counter that doesn't turn wrenches and try to upsell you transmission flushes, coolant or brake fluid flushes, air filters without looking at it, don't let them talk you into something you don't need. Most not all dealerships are good. But some are just as bad as jiffy lube who hires anyone to change oil. And sells you filtered recycled used motor oil will do anything to make their commission higher. And ask them if they make commission or hourly wages.

[@christianobrien4465]

Excellent

[@flippintobyland7257]

The real cause is the EPA

[@NemesisConfirmed]

Can a bad purge valve cause this? My journey has power and is very responsive, it also has the code for a bad purge valve.

[@2010nelly2010]

I have a 2008 infiniti Ex35 which had the P0420 code. Was diagnosed that the cat's needed to be replaced, as appeared to be clogged. Replaced cat's. However, I now have extremely, poor gas mileage. There are no error codes. Any idea what is wrong? I am so confused that the cat's were replaced and now my fuel use is up by 30%.

[@alirazmjou2149]

Thank you so much for this video متشکرم

[@nedasher116]

I have both should I try new 02s

[@pa.fishpreacher6166]

if it is stripped threads can the 02 sensor still be replaced?

[@familygeek788]

Would this cause loss of power steering if the system is electriconic and advacetrac light to come on

[@thomasshannon9662]

In many Fords, the MAF can give you a fit and make you think you have CAT issues. In my case, the MAF was fine but the Baro sensor was bad and unfortunately the sensor os a 3 in 1 sensor.

[@tyronewalker5764]

Thank you so very for explaining this. I'll get a P0420 error, then it will disappear for weeks or months. My 2k Dodge Dakota has 2 O2 sensors.

[@oneway1811]

My Nissan nv200 started to doing it as well it goes on and off already pass smog

[@kannarianulmer5686]

mines came on after getting a oil change, what could the problem be?

[@robinwilliams5841]

I got a code po430 bank 1 on my 2014 Kia rio. I’ve changed the front catalytic converter and o2senor now it’s throwing a p420. Any ideas???

[@Pallidus_Rider]

I replaced the catalytic converter in my 03 Corolla in 2019. I just got the P0420 code again. I suspect that the oil consumption and burning is the cause. Any thoughts on Cataclean?

[@sleepwalking117]

I got some strange readings on for my p0420 sensor. The cat gets a green check mark and the 02S does as well but the EVAP isn't hitting the mark. Trying to get this car smog ready and out of Non Op but this is the wall I'm hitting. Changing spark plugs tomorrow but idk if it'll help.

[@MotorAgeMagazine]

I think you are referring to the monitor status for the various systems. The EVAP monitor can be the hardest to set. What kind of vehicle is it and are there any codes?

[@user-ch9bz9jp1v]

Good day thank you for your help I need to ask you some explanation about a car that have no problems but don't have a power enough to climb up the street .thank you

[@MotorAgeMagazine]

If it has no power than it has a problem. Any work done recently? Have you tried dropping the exhaust ahead of the catalytic converter to see if power is restored? What tests have you done?

[@geovanybonilla2244]

Hi Pete, how are you? I would like to know how much back pressure there should be in the system when the pressure transducer is used, many information recommends one psi at idle and no more than three psi at 2,500 RPM, is this correct? Thank you .

[@MotorAgeMagazine]

Those numbers are considered "standards" but I like to see very little at idle. When using the pressure transducer, I'm looking at it building over time, especially when performing a snap-throttle test. That is where you'll see the restrictions show themselves.

[@D...M...A...]

@@MotorAgeMagazine Dear sir , Cat on a 2012 Camry , 150,000 miles ... Burned oil since new to the tune of couple of quarts in between its regular 10k mile oil changes... Slow , long time oil contamination / poisoning of the cat ? Thats my conclusion , what do you think... ?

[@MotorAgeMagazine]

@@D...M...A... Absolutely! I'd say try to clean it first using a fuel induction cleaner but with 150k on it, it's time to replace it.

[@D...M...A...]

@@MotorAgeMagazine We're on Cat -o- clean # 6 thru the system , seems to be improving ... Triggering less #s of codes (420 ) per tank ... About to give up and change it , but it keeps teasing me with improvement... Thank you kindly for your reply and expertise ...

[@MeachPango]

Could a dual fuel propane system (that has been removed) foul the converters?

[@amandaeaton3919]

Also, should I run some heat through the truck because I have been running crappy gas for economy and this problem started after the outside Temps reached -15 and it wouldn't start. I "think" it's the exhaust leak, but water in the motor that froze probably added to the issue

[@howdareyu]

On a 2006 ford crown Victoria police interceptor I have a PO420 code catalyst below threshold. I smell an exhaust leak, and per the scan tool one sensor is dead, and cat has reached 1650 degrees. Would you say that was enough to damage the cat beyond saving? And I'm taking it the leak gave too much air, this too much temperature? Pleeeeaaaase help! I know you kind of answered my question in the video

[@MotorAgeMagazine]

Take care of what you definitely know is bad, clear the code and rerun the monitor. It is possible that the cat overheated but the only way to know for sure is to take it off and look through it OR use a thermal imaging camera to look for signs of melted substrate. Yes, air leaks are like excess fuel - either causes the cat to run hot.

[@StationRussification]

Long Term is the window of time the adaptive memory dictates the fuel trim, Short Term is live data calculating to learn the parameters for the adaptive memory to update the Long Term. The O2 sensor signals rich below .45 volts & lean above .45. The Engine Controller only cares about that threshold & uses that to determine fuel trim. .. in other words the computer calculates the % of time that the O2 sensor is past the threshold of .45 volts & does that each time the threshold is crossed.

[@terrybyrd3738]

My check engine light hasn't turned off in ten + years. I finally gave up on it. I think they exist to get people to empty their wallets on worries that don't exist.

[@wanders278]

@@user-2Hteyasizyc you sound like a scammer

[@ExploringCabinsandMines]

I've come to the same conclusion, until it effects engine function ignore the pretty lights.

[@parexc07]

Bad CAT... Just check your cars insurance and park it on a busy city corner over night. The minute mechanics will remove it for free....

[@MotorAgeMagazine]

😊

[@universalstudiosshorts9963]

That happened to me

[@MrJOHNY347]

I sprayed down the flex pipe with soapy water and it started to bubble up .I currently have a p0420 code .I’m going to repair the flex pipe and hopefully that will solve my CEL.

[@MotorAgeMagazine]

Very likely it will. That is letting air in and throwing of what the sensors are seeing and could even cause the cat to overheat because of the leaning out of the feed gasses. Let me know!

[@deandreissadasf460]

hey did you ever fix the flex?

[@knifeknerdreviews4609]

So I have a P0430 code on my FJ Cruiser, I can make the code go away with an "Italian Tuneup" which gets me through inspection every time however I have grown tired of seeing the christmas tree on my dash every so often so I appreciate these tips in both the video and the comment section. I happen to know the valve cover gaskets leak a certain amount of oil into the spark plug chambers, is it possible this is the ultimate cause of it? I have been building a parts list to replace a lot of the maintenance parts on top of the engine when I do the valve covers and once I have done all of that, if the code persists, I figure I will tackle the air fuel and 02 sensors next, then finally if it continues the Cat will be the last piece of the puzzle. Truck idles and runs like it's brand new so I rather doubt the Cat is actually bad.

[@Mantis858585]

Have you tried a cat cleaner?

[@ericmol2614]

I have the code thing. But an expert said he could fix it for under$220. So then I'm thinking that it could be the O2 sensor because my mileage is about 178k and they might go out around 150k or sooner. I saw one for about$170 and the guy said he could fix the problem for $220 so I think maybe that's what he was going to do. I hope that's the problem then I could just do it myself.

[@MotorAgeMagazine]

Be careful - without performing a proper diagnosis, no one can tell you what they can do to fix it. With the mileage on your engine, it could be a number of possible causes, including the converter. Seek out a more professional diagnostician.

[@pontificusvascillious5287]

thanks for the great explanation ... there MUST be a better way ... amazing engineering to make a car a car ... but it's WAY too complicated ... and expensive ...

[@jeffsond]

Would the PO420 cause the car to go into limp mode? The vehicle is running terrible and won’t shift out of 2 or maybe it’s 3 gear that it’s in. Starts and runs ok until you start driving it. It did pull a PO420 code. Cats were changed 1 1/2-2 years ago. Could it be the oxygen sensors??

[@ekpemawulidaniel35]

I hve small leaks around the manifold is it the cause of my P0240 code( cruze)

[@wazzabanzook5028]

my 2006 honda civic does have the P0420 code , it is sluggish especially take off and feels like it has power loss, also fuel consumption is very high. so is that most likely a blocked or failed Cat ?

[@MotorAgeMagazine]

That would certainly be my first test.

[@falcorthewonderdog2758]

My experience with p0420 is usually a ignition issue or an exhaust leak at the manifold. There are other possibilities but in GM platforms it's more common to have high mileage plugs or worn / lose exhaust pipe to manifold seals.

[@travisblankenship1495]

I have an small crack in my exhaust manifold. Jeep xj. Code just happened after a new ECU was installed...

[@Nomenclatureish]

Probably not the cause but my ‘98 Corolla was less than a year old-still at the Dealership Service stage-when someone forgot to re-fill the oil tank after a change. My mechanic kindly rebuilt the engine and the code began soon after.

[@cruz7073]

I got P0420 on my ‘02 Honda Accord and it’s supposedly the Catalytic converter i wouldn’t be surprised if the first owner still has the stock cat after all these years but my new one is coming in on Friday I’m hoping it fixes a really bad overheating problem I’m having

[@Hero-hb9lu]

⁠@@cruz7073Did the new catalytic converter fix the problem? Having the same issue on a 2001 Accord lx.

[@liarliar1408]

2011 Camry le all stock n 390k miles all original parts. Could not go up a hill but flat driving ok. Seems to lack HP too. Never change trannie fluid, so I'm I'm getting code for torque converter n code for shift selinoid. Non of this has to do with emission right? Check light on n off n p0420 for cat was another code. With these Toyotas, the manufacturer messed up as it is known to lose oil. The pcv needs to be replaced to solve this. Since it is leaking oil but not dripping on the ground, the oil goes to the exhaust n can clog the cat. I had a smog ran with co2 being 0 but hc was 15 so it failed emissions. Now getting a new cat would not solve the problem. Maybe I'll pass smog upon getting a new cat n can drive for 2 more years b4 I'm up for another smog. Eventually the new cat will get clog up as well so he's right when he said that the underlying issue needs to be addressed first. Plus with mine at 390k miles, maybe it is time for a new cat or get a newer car. Over 2 Grand just to get a cat replacement with mine. Fixing cost more than the value of the car so why bother? An option is to get cataclean bottle as it may help with the carbon build up n hoping to get that smog pass. California I tell ya. If this was MN where no smog is needed, I can go as high as 600k with this gifted vehicle. Oh n another way to test to see if your cat is good or not is to get a heated thermal laser scanner. You take the reading of the top of the cat, the middle, n the back end. Top should be hot, middle hottest n the back should be cooler. If the Front is the hottest then you have a clogged cat as heat has no way to get out from the backend so it travels to the front n that can do damage to whatever parts there are on the front like header n pump n whatnot to give you an overheating vehicle too.

[@e-zward9019]

Lacquer thinner fixed mine.

[@timbenson428]

Finally....a REAL teacher who even speaks English that is understandable. There are dozens of these video's here on KZbin that are pure GIBBERISH....or.... BROKEN ENGLISH as I never understood a word. YOU are a great teacher sir. Thank you.....

[@MotorAgeMagazine]

Thank you for the compliment! Glad you're enjoying - and learning from - the videos.

[@chaseboy225]

Carbon buildup can also trigger Code P0420. My 2014 Jeep Grand Cherokee Laredo threw up the code even tho the o2 sensors and cats were good. So I thought hmmm what if it's carbon buildup? Got 2 cans of Seafoam intake cleaner, followed directions and after it blew all the carbon out the check engine light shut off and P0420 was gone forever

[@Scaled-DownReptiles]

In my experience most of the time I’ve seen these codes it did end up being a bad cat but I have saved my customers a lot of money on occasions where it ended up being something else

[@christopherfoxwallace1291]

You haven't gone far down the rabbit hole of OBD diagnostics. I'm sure you find bad Cats BUT that's not what his message is. Like the Trainer has said "Cats are built for a lifetime. It may go bad, do you just replace parts or find out why it went bad to fix the problem." I'm putting my money on the fact that a Technician finds what has caused it to go bad. Any takers? Trust the code, check the circuit , Make the repair.

[@christopherfoxwallace1291]

It's always something else. Parts seldom just go bad. There is a cause for everything.

[@DJ-tn7vj]

@@christopherfoxwallace1291 💯 agree with you on this but this code is a hard one to crack due to the amount of inputs that can trigger it. I have tried multiple times to get rid of it even with a good cat and had to try various things to get it remove.

[@MrKamikazeLee]

It looks like getting the job done right.

[@NOM145]

@@christopherfoxwallace1291 I've replaced the (2) converters on a 99 4runner 4 times in 3 years. I gave up after 3 sets in the first 4 months i had it. Nearly one thousand into diag else where the last 2 years and no luck. I take it in specifically asking for why its damaging the cats and they come back with "replace them." Or my favorite "P0420 is always a converter failure." I pay the diag and onto the next shop. As much as I don't want to pay because my question goes unanswered, they still worked on it so I respect that. I gave the first shop that replaced them a second chance and they installed their best cats yesterday. 4 hours later it was back...in for a diag next week. Fun times.

[@peterarries7879]

Brilliant

[@kermitefrog64]

My P0430 code has become intermittent. Today was cool outside and tonight the temperature is 45 degrees outside. And the code on my dash went off. I just replaced my O2 sensor 2 weeks ago and it seemed to work because there was no engine code. Then 2 days ago the light came on and now tonight the check engine light was off again.

[@terrencecarter27]

Hey I've question , can you go into more detail regarding the vaccum technique it was very unique. Because I don't have a shop or such with high end equipment. I do have a borascope but no gas machine, I. More of a Diy person but I'd like to learn.

[@MotorAgeMagazine]

I don't take credit for the techique, as I shared in the video. Your shop vac has two ports - an inlet and an outlet. The hose is typically attached to the inlet (vacuum side) and the vacuum is vented through the outlet. To use it to pressurize the exhaust, simply move the hose from one port to the other and attach the (now) pressure side to the exhaust, using duct tape or something similar to keep it in place. Then turn it on and use a mix of soapy water to mist the exhaust - and look for the bubbles!

[@MotorAgeMagazine]

@The Edwin Manna Filez If power in drive is normal, then I doubt you have an exhaust restriction. What work was done recently and are there any codes stored in the ECM?

[@MotorAgeMagazine]

@The Edwin Manna Filez Have you performed a cylinder compression test? I use my scope to do a relative compression test first - so if you have one, or access to one, use that technique. It's much faster.

[@MotorAgeMagazine]

@The Edwin Manna Filez I'd still do a compression test but regardless, you'll have to get into the engine to fix that. The oil passing through the exhaust will certainly poison the catalytic converter and cause that P0420, too.

[@ronaldmahoney1283]

If you replace a bad computer, should I reflash the new computer to clear the 420 code when everything else has been done?

[@MotorAgeMagazine]

The code should not set in the replacement ECM unless the fault still exists. Be careful condemning a computer - they are rarely at fault.

[@JB91710]

First thing to ask yourself is, "Did my battery go dead or did I replace it?" Sometimes you have to perform a "Drive Cycle" specifically for your car so your computer can run a "Readiness Test."

[@kariniemannfuss9208]

What do you mean by drive cycle? Our battery went dead over winter. Its been recharged but the truck will only turn over, not start. 2015 GMC Diesel.

[@JB91710]

@@kariniemannfuss9208 You are a prime candidate. Just Google " Drive Cycle" for you vehicle. You could get one from GMC or your mechanic. On my Tahoe I had to let it idle at a specific RPM for a period of time from a cold start with a number of electrical items turned on and drive it a certain way to allow the computer to scan all sensors to know that everything was working properly. The codes switched off and I was able to get the emissions checked. As far as the no start, you'd have to check with diesel forums with your specific issues. Sounds like a computer communication problem. With no power for an extended period of time, the computer might need to be reprogrammed.