Omg. Finally someone who knows what they are taking about, and clearly explains what he is doing. Best part is that he shows what a bad cat looks like, and what a good system should look like on the OBD. Very helpful. Thanks

This is how all KZfaq videos should be. Clear, intelligent, demonstrative. Rockstar quality.

Hi Eric! It's Shep in Florida.(Retired tech) 3 years ago I replaced the engine (2.2 4cyl) in my 2000 S10 with a new (not reman) engine from GM. I replaced the fuel injectors and pressure regulator (Sorenson). o2 sensors (AC Delco). And cat (Walker). 11 months later ap0420 code appeared.The truck runs like new (it should with a new engine). I have no vac or exhaust leaks (vac at 18 in' average and rock steady) No misfires and fuel pressure is normal. NO other codes,and gas mileage is good. AutoZone replaced the cat at no charge. Last week the p0420 code appeared again.I ran a live data test. The U/S sensor switched as expected. The post sensor switched between .11--.95 volts. AutoZone replaced the cat again and the post sensor now reads .73--.78 at highway speeds and .44--.47 at idle and right around .50--.54 volts at 35--45 mph. My GM tech friends say I need to install a factory cat ($1000--$2000).My auto tech instructor (the 1 who taught me 30 years ago and is still teaching) and my independent tech friends say that's nuts and a Walker cat ($179) or any cat should be fine. Any ideas? I was always taught that cats don't just die,they're murdered. Florida has no emission testing (except for Miami) but a mil drives me nuts. Thanx and G-d bless.

Hi Eric, I really love your videos, as I've been searching them for an answer as to why my Mazda Protege 2000 loses power when it warms up. It runs great though, smooth idle and purrs nicely, just has no pull and goes so slow. After watching your videos I now know it's nothing to do with my exhaust obstruction, thanks. So now to watch more of your videos to find out what the issue is.

You, sir are a national treasure. Thank you for so much great information! I've used your videos many times to handle work I would've otherwise had to pay someone to do. Thank you, thank you, thank you.

I had this code on one bank (V6 engine) for close to a year, all O2 sensors checked out fine...also started getting lean/rich codes which made me check for vacuum leaks(all good) & clean my idle control valve because the car started shutting down when idling, no change then decided it must be a bad MAF. bought a cheaper Chinese model for $45 on eBay vs OEM pricing...cleared codes and drove for a couple of days or 70-90 miles...rescanned and everything was good to go including smog readiness. Just passed smog...converter was fine but bad MAF was sending false air readings to the ECU, thus flowing more fuel which cooled the converter aka not warmed up enough (below threshold). Fuel economy was not good...but now i can drive 1/4 tank to and from work for 3 days on a v6.

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.

Very good video! My son has the same code, and I’m trying to figure it out. I’m changing the 2 downstream O2 sensors to see if one or 2 might be lazy (wishful thinking, I know) now I’ll have to bring my infrared thermometer out and do the test! Also, I’ll monitor the voltage swings as well. Thanks for the video, you just enlightened me!

No, cats work like I explained in the video and that is their main purpose. They also help with HC and CO but those are secondary effects.

This was really informative and professional. You seem like a mechanic and youtuber who cares about their work. Thanks for the information, this will definitely help me with my maxima I've been having issues with.

Great information. Thanks for the details on how to track down the source of the P0420 code, because obviously I don't want to have to replace my cat if it's just an O2 sensor.

Thanks.Your right Eric.I like the custom list.I will try that,as I have that same Actron.The Ocilliscope reading for O2 Sensors 1&2 would show rapid huge fluctuations on a bad cat.Good cat, only O2 1 would change rapidly but even, and 2 slow even changes.That's from Pro Demand DTC PO420.A quick test with a vac. gauge can also verify a clogged cat. At start up the reading will be 18-22 in hg,then as back pressure builds, it drops a lot.Then engine will have no power or shut off.The smell of rotten eggs is also a symptom.

Eric, Thank you explaining this! I known for a long time that laser temp trick, but I never used it or seem the temps from it. This is going to be very helpful this weekend!

I end up on your videos often and it resolves my problem or otherwise educates me. Thank you for what you do.

I was taught that in a 3 way cat the first section was for Nox and the rear section was for HC and CO. Some manufacturers used mini Cats just off the manifolds for Nox and they put bigger cats downstream for CO and HC. Probably more then you wanted to get into, on a basic understanding video. I did not know about the X in Nox. Good video Eric!

Ended up taking in the truck and the cat was replaced under warranty. Thanks for the video and all your info. Saved me a ton :)

Learnt this: Upstream O2 sensor switches voltage all over. Downstream O2 sensor voltage should be more steady.

Dude! You are a marksman!😃 On all aspects of the word. Pinpointed the problem ...but also that steady hand aiming the laser between that tiny space with almost No wobble while lying on the ground side ways... that’s that Sniper-Stuff right there...👌🏾😎

Got a P0430 and was wondering what it meant. You've simply explained it. Thank you for the upload and sharing your knowledge. Keep them coming cause we'd be lost without you.

THANK YOU!!! Warmed up, at 2500rpms the oxygen sensors are reading; (bank;sensor#) range of movement, Fuel trim % Upstream (before cat) (1;1) 0.20 => 0.80, -3.1 => 8.6 (1;2) 0.20 => 0.32, -3.1 => 7.0 Downstream (after cat) (2:1) 0.16 => 0.80, -5.5 => 5.5 Exhaust pipe temp after cat is only 30deg Fahrenheit greater than pipe temp leading into cat So, because of your help I am able to start with replacing the cat! 2002 Acura RL, trouble codes (in order) P0118 (seems fixed by replacing leaky rad cap), P0420, P1486 (seems fixed too).

note to this video. if you have a air fuel ratio sensor it will read different. this is only for o2 sensors

Great video! I really appreciate you taking the time to document and explain various diagnostic and repair procedures. I thought I might point out something. Not a point of criticism, just trying to help a fellow gear head out. At 7:29 you talk about trying to "shoot the laser between the heat shields." The laser is just a guide for you to know where you are aiming. The infrared sensor below the laser returns the temperature value. Also, the sensor measures a circular area, the further away you are from the target the larger the area. The value returned will be a rough average of that area. It is important to note that the laser will point above, not directly at, the center of this area. On a high quality IR Thermometer you can expect the circle to be about 10:1, distance to diameter (aka distance to spot or D:S ratio). In other words, at 18" distance to target the circular area you are measuring will be approximately 1.8" in diameter. Check your users manual for both the off set distance of the laser center line to the IR center line and the distance to diameter ratio.

Hi Eric Thank you Eric! Thank you for the simple way to test for a bad cat. My daughters car is a 2005 Subaru Legacy with the infamous P0420 code. I used my scan tool and the infrared thermometer and got the same results. However at least the driver side cat is lighting off, only one to worry about. This saved me from wasting 70.00 for a rear o2 sensor.

I just came from another video talking about this code who suggested just tossing a bunch of gaskets at the intake and hoping it was just a leak. Thank you for in depth descriptions talking about how to diagnose the cat

Eric Ive been watching your videos for years and have been inspired but not yet been in a situation where I had to try out your basic tips. However I have recently had the P0420 code and have watched a number of videos on the code and was thinking I would need to take the car into the garage to see if it was a sensor or cat issue as none of the other videos gave a easy way to check and test that is until I saw this video as I have live data on my scan tool I did this test on my car and BINGO exactly the same issue so I went to the scrap yard and picked up a replacement cat now to get changing it. You are a star mate.

Side note, also make a heat shield to redirect the gases away from other components if necessary. The hole for the o2 sensor points right at some rubber hoses so I redirected the gasses with a makeshift aluminum sheeting I had. Not Ideal but I only went about 500 feet to do the test a replace the o2 sensor.

I got an abandoned 01 Xterra from a tow-yard for $550 because of the P0420 code in Colorado where they do emission test. After using an Auterra to diagnose the issue at the lot and the Autel tool I use at work once I purchased the vehicle, I was able to identify a failed front cat as well as an intermittent failure on the front O2 sensor. $100 catalytic converter, $100 Bosch 02 sensor and $150 in labor later and it's running like a champ once again. I tried the $20 eBay "Chinesium" O2 sensor, which lasted two weeks before burning out again, so best to get OE quality parts. It was funny because once everything was bolted up and I fired it up and revved it all the sooty black water got pushed out the pipe. Soon after the rear cat temperatures and O2 values began looking right, so I lucked out with it only being half-plugged (due to a leaky valve cover gasket that was dripping oil onto the front cat). No leaks or issues ever since. Best of all, no engine money light. This video came in quite handy through that ordeal several months ago, so thanks for your help. This was the first vehicle I ever had to do emissions work on, and the last time I worked on a KA24DE it was in a 92 that didn't have hardly any emission devices. A lot has changed in nine years, thankfully it wasn't that hard to mend the issue. The hardest part was all the rusted and heat-welded bolts that had to be cut off with a angle grinder. I must have wasted two weeks trying to PB-blaster soak them and hitting it with the breaker bar for nothing. The ones that gave usually just ripped the heads off the bolts, so just cut it off and save time.

98 Ford Ranger 3.0 inlet temperature on forward converter is 100° higher than the outlet. Will be checking back pressure. Truck sometimes stalls while driving or stopped. No check engine light or codes on this. You have great videos and tips

Good video, very handy to know. But I've got a BMW and there's a warning light on the dash saying "catalyst" I have no idea what it is. If you can tell me please. But keen to get dirty to find out. Lol cheers

have to be careful with a lazer style temp gage, most people think that where the lazer hits is where the temp is being read. Actually the area being read is larger than just wat the lazer hits and the farther you get away the larger the area being read. Think of it more like a flashlight not a lazer. if you want to pin point you got to get super close. Most of this should be covered in manual.

Eric, you are awesome. This code has been haunting my Accord for years. Now that I have a scan tool with live data I'm going to perform this check my next day off.

Thanks man, a P0421 code came up with my car. The o2 sensors are both fluctuating between .1 to .9. Now I'm pretty sure my catalytic converter needs to be changed. Great video, thanks!

Eric you gotta open your own mechanic school. Teach people man you know your stuff. Keep up the good work! Love the videos.

Thanks Eric, a video I can understand. No waveforms, short term fuel trend or long term fuel trend.

Hi Eric, I hope you still read old videos comments as I have an interesting story on a catalytic converter: My car is a 1994 Autobianchi Y10, OBD1 single point fuel injected, bought new back then. The cat is still the oem one but it stopped working many years ago. The car was starting to burn oil and I diagnosed bad valve seals. I decided to do a head job, so replaced the seals, lapped valves, machined the surface for the new head gasket and finally put back the head AND (this is important for the story) I changed the paper seals for the throttle body. Started the car and immediately something was wrong, it runned very rough and had problems to stay at levelled idle. I noticed that the engine was running hot, I took my temperature gun to check exhaust temperatures and they were very hot, even at the muffler. I decided to verify temperature before the cat, it was around 220 degrees C (428 F) and 400+ C (750+ F) after the cat. So.. the cat was working! I then discovered that one of the paper gaskets for the throttle body was the wrong one so it had a bad vacuum leak. I replaced the gasket, solved the problem with the engine but.. cat stopped working again, now I have barely 180 C (356 F) before cat, and around 150 C (300 F) after cat. It looks like that the exhaust is not getting at the right temperature to make the cat working properly.

I appreciate when Eric upload a video about. A car problem. Usually when you have. P0420 is because the catalytic converter is done, is dead it’s not goba work no matter what you do. I can tell that by personal experience, it happen to me twice.

I've got a crack in my exhaust manifold 2001 Honda Civic I was told that I should just replace the whole thing with the catalytic converter and manifold all in one piece. If on the road too long I get a check engine light p1361 top dead center sensor noise. Should I replace O2 sensor and camshaft position sensor when replacing this manifold and catalytic converter

Very informative Eric. I learned something today. Now I can go home and have a beer!

I’ve already subscribed, but I would subscribe again over this. Thank you so much for posting this along with the explanations. You saved me a bunch of money - I hope I can post something reflecting that savings. And not only did you save me money, but I learned a ton. Now I feel I have a more solid foundation of emissions. Thank you sir.

Well you just saved me thousands. Do all my work and the car runs stellar but had an 02 code off and on and looked under a nice scanner and wouldnt you know. No voltage to upstream 02 sensor, cracked downpipe and scanner wont read post cat 02. Im stumped as when i re did emissions my car did worse than first test. My guess is cat is mostly plugged as it doesnt like over 4k rpms, my nox is the only reading failing. I dont have excessive coolant temps but maybe 200 in my engine on a 190 t stat. My fuel trims seem really off and performance seems worse after its been driving all day. Oh and cant get any more temps so about to lose out on a nice car. May get a digital thermostat tonight and check readings. If its good then idk what else will cause nox levels to double. Also HC and CO readings were up there but still in passing limits. Had 2 mk3s jettas before and bost fast passed and practically no tailpipe emissions when they were working

Thank you so much! This was exactly the case with my van.

Thanks Eric, I did both of these tests on my 2005 Honda Odyssey and I do need a Cat. Do you have any recommendations other than OEM?

Thank you so much for this awesome video. I don't have a live instrument reader but I did take the temperatures of both my catalytic converters. The one coming from the engine has a temp of about 500 degrees going in and only about 230 coming out. The one under my car is about 220 going in and 220 going out. Am I right to believe that it is the cat coming from the exhaust manifold that is defective? Thank you for your help

Thank you for all your time and well intentions for our lives 🎉

Excellent video! Clear, concise, pure information. Thank you.

Thanks bro! Great video! Helped better understand my scan tool and the infrared scan as well! Was sure what I was looking for in the scan tool.

Thanks for your specifics & clear communication! Always glad to hear your expert opinion. My 2012 Kia Rio is already showing check engine light due to P0420 after passing only 98K miles. I've been able to clear code 0420 using high octane gas plus using a bottle of CRC G2P brand fuel emissions test formula, once per month. What's your thoughts regarding CRC G2P bottles, and a Rio's cat-converter going bad after only 98K miles? Thanks much. ~Shawn

Excellent video, subscription earned! Went through an ordeal this last smog test. Ended up being a TPS sensor that wasn't throwing a code. Now just more interested in understanding how all these things work together.

Good job on showing what a good cat does not only a bad cat

what model actron are you using? great videos! thank you for your help.

Very good info I sorta knew this already from reading some articles after failing emissions however I had to research for days to find all that here is presented in a 10 min video which speaks to the amazing... job done here... As for my problem I've pretty much narrowed it down to one of the cats ( I also had many exhaust leaks but they don't seem to be the issue) but no idea which one... I doubt it's both....As my emissions aren't terrible just my nox is kinda high... at time and sometimes just barely fails... Probably gonna end taking a thermometer to both cats and see which one seems weak... to narrow it down... I've heard that the back cat is responsible for nox but I've also heard the opposite and what seems most likely true that it varies by model....... precat vs main cat.. I highly suspect main instead of pre on my model... but I'm gonna check first as I don't wanna replace wrong part if I don't need because Cali approved CARB cats are like 500$ a piece!!...

As has been mentioned by Eric, you need to know about what you are working on. The three-way-catalytic converter (TWC) is part of a whole engine fuel/exhaust system design. With a proper functioning engine system, today's TWC are designed to operate for the life of the car and meet emissions requirements. The best way to test a TWC is with an exhaust gas analyzer (which are expensive) and proper testing methods of which there are several. If a TWC is determined to be defective, the cause of the failure must first be determined. Not to do effective diagnosis and repair of the root cause of TWC failure can result in replacement failure soon after. California emissions testing is super tough and replacement TWC must meet those requirements. Even replacing a TWC in California must meet strict requirements. In some areas of the U.S. to even replace a TWC requires a special certification. Go to any auto parts web site (try rockauto.com) and notice most of their TWC offerings cannot be sold in California. OEMs are often what is needed. For a comprehensive discussion on engine emissions design and catalytic converter info and testing go to this link. This information is also quite helpful in avoiding a TWC failure in the first place. www.lbcc.edu/attc/documents/BAR-2011-CAT-testing-methods.pdf

I was given error code P0430 for my Honda Accord V6, I'm thinking it's the converter, I don't want to change it at least not now, cause it's pretty expensive. Is there any problem if I use the car like this till I can get enough money to fix it? i don't want to risk damaging something else.

From what I was taught catalytic converters when operating properly will have a hotter temp on the output end than the input end.

I thank you sir for your knowledge you have shared to us, so we have now an idea to diagnose and fix our equipment, God bless you because you share your talent.

Hey Eric, I'm having the P0420 code in my bmw e46. My 1st o2 sensor is jumping around, and the 2nd one is staying at around .7-.75 when reving around 2-2.5k rpm. I'm trying to pass emissions, and i'm worried about failing, if i perhaps used the lacquer thinner solution, do you think that might clear it up? Anyone else - thoughts?

very knowledgeable video. good job eric. keep making them, i learned a lot from this it and u helped me figure out what was wrong with my wrangler. u saved me $744.32

Excellent video, very informative, thanks.

Great videos! I have a bad cat which melted my 02 sensor to its harness. Now I have a bad harness which I cut off. What is the best way to put a new harness on for my 02 sensor? Thanks!

THanks Eric. Wife's Kia Rondo just threw a P0420. Time to do exactly as you described. Thanks for the quick tip.

That infrared thermometer help me you so much thank you for the tip

A stick wedged between the seat and the pedal. Very high tech

Great video Eric! I'm diagnosing a P0420 on a 2012 Altima right now. All your info is super helpful!

Thank you for your explanation, really hope I just have a bad upstream 02 sensor, my 2006 honda pilot has a p0420 code but now I know how to diagnose at least.

My car sounds really loud now, when I drive it. is this a sign that I need a new catalyct converter?

i failed my smog check and the only thing was the NOx test, yet nothing is or was wrong with my car. i went back the next day and passed without any work i just said they fixed it.

I cleaned 4.6 GT Mustang (85k miles) by putting one gallon of lacquer thinner into a half a tank of gas about 8 gallons. I added the lacquer thinner with funnel at a rest area on the interstate. Run it all out with overdrive off and punch it a few times "Do not" just put the lacquer thinner in and let it set around with normal driving to work, run it all out right after adding it. I did this twice the first time did stop the p420 code but the second time my scan tool shown a much steadier high voltage with the down stream o2 sensor. The other bank did not clean up as I found out after taking it off that the catalyst material had disintegrated. The side that did clean up had no build up of carbon the catalyst material was tan in color same as the new cats that I replaced them with. Here a gallon of lacquer thinner is $16.00. I am going to use this lacquer thinner method of cleaning every so often on my new cats. Depending what the scan tools tells me what the downstream o2 sensor is reporting. Somewhere between 10k and 20k will get the first cleaning to keep the carbon from building up. I do use Lucas gas treatment often and that will keep my engine cleaner but makes the cats work harder.

Hey Eric, have you ever managed to resolve hesitation issues of this engine? I have a similar issue on EJ20 impreza.

I have to say something. The downstream o2 sensor is to monitor the efficency of the oxidizing converter. Not the reducing catalyst. The reducing catalyst reduces the nox and there is NO field test for this without a dyno. The oxidizing catalyst reduces co and hc.

you need to explain to people that the exaust temp. should be hotter at the rear of the convert than at the front. its should be about 100 - 150 degress hotter at the rear than the front. you left out the specs. thanks

great video and great info! My 01 Impreza 2.2L just threw a p0420. Thanks to your info and Scotty Kilmer I now know how to diagnose(you) and attempt a cheap fix(scotty) either way I will be replacing the cats with new units since the flanges are pretty corroded.

The secondary O2 sensor readings on the Odyssey seemed to be switching just as much as on the Subaru, the numbers were just higher. Does that go more towards the accuracy and sensitivity of the scan tool that's used?

To bad I live here in TEXAS were we do have emissions test's on whatever vehicles yearly and it could be a pain to pass inspection.

Cool. I was just proud of myself when I did my cat repair and wanted to share.

Hi Eric, great video, as always. Thanks for the information. I notice that you were using a Actron scanner, I have one too but I can't get the first sensor to show the units in Volts. It only displays the units in mA. The second sensor shows the units in V. Is there anything you can suggest so that I can compare both sensors using the same units? Thanks again

I just did this test on my 03 Acura cl and I was surprised I have no check engine light but the inlet on the catalytic converter was about 150 degrees hotter than the outlet so does that mean its bad?

Okay, this is for all the people who did this test, then rushed out and replaced their bad CCs and then weeks or months later it is bad again. Your catalytic converter didn't go bad just because it was old or whatever. It went bad because SOMETHING ELSE IS WRONG too. If you don't fix that, you'll just keep blowing your new converters. Start looking for things that cause the engine to run too rich or too lean, burning oil, etc.

I live in Florida and I'm glad we don't have emissions testing. I think my passenger side cat is failing(or o2 Could be bad haven't gotten under my truck yet). But either way, I get to it when i get to it no rush.

Had a couple videos that have been very helpful. In this case, ended up being an exhaust leak as the readings panned out based on this video and moved on.

Hey Eric I’ve got a 2000 Chevy Silverado it’s got the 4.3 v6 and my issue is sometimes my Truck will hesitate on take off and tbh it just doesn’t seem to run all that well in my opinion..I know these engines don’t have a whole lot of get up and go power but the Truck just seems a little more sluggish than it should be. It’s had a complete tune up and is throwing no fault codes at all. It’s got 122k miles on it. Would you have any ideas as to what could be wrong with this Truck of mine? Thank you!

You have a clogged cat if: 1 your car has been burning oil for months and months. Usually you get the P0420 code. 2 your gas mileage has gotten 20% worse. When your computer senses a rich burn, it leans out your mix. Lean means sends more gas and results are that the mpg is hurt. 3 you can not accelerate on to an on ramp to a hwy. The car boggs down due to restricted exhaust flow.

Eric, just a quick note- I hope you realize that the laser is not what measures temperature, it's just a laser pointer to show you the center of the area that you're measuring temperature at. Also, they typically have a distance to spot ratio, typically like 8:1, so at 8" you're measuring a spot 1" in diameter. The way you did your test I would guess you measured about a 2" in diameter spot, so mostly heat shield temperature... so if you just drove the car, and most converters are mounted longitudinally I'd bet that even a bad converter would measure with the front cooler than the rear due to airflow

Just a Heads up when using a IR heat gun. That laser dot is measuring a much larger spot then the size of the laser dot and it changes depending on how close it is. it may be the size of a quarter or larger. So if its right next to the heat shield its averaging the temp of the heat shield and the pipe and maybe even the floorboard behind it. The cheaper the heat gun the larger the spot. Also the color and type of material effects the temp.

Eric, if you were to recommend a catalytic converter cleaner that goes in your gas tank, which one do you think it's the best at the auto parts store?

I work on the old school cars 60-70s collectable stuff. My daily driver bought the hems manuals even they don't go into the detail you do bud. Teach a shop classic to have more capable techs, I worked for dealership wasn't my thing

The video is informative, but, if the issue that destroyed the Catalytic converter is not found and repaired, any replacement catalytic converter will fail also. Problems with engine performance cause failures. If the problem is caught early on, failure can be prevented. They do not wear out. So, did you find what damaged the catalytic converter? I doubt it was curiosity. Google "engineers perspective on P0420" and click on the link to subaruoutback org .

O.k. Eric, I definitely need some help on this 1... I've got a 92 toyota paseo (automatic trans) and it failed CA emissions for high NOx @ the 25 mph portion. The engine stumbles and dies when direct vacuum is applied to the egr valve and ive got vacuum at the intake source. I've already replaced all the vacuum lines... So it seems I'm left with the vacuum switching/ egr vacuum control solenoid as the culprit... Question is how do I test that? Being an automatic trans it's got 3 connectors and 6 vacuum connectors. My wife and I are down to 1 car now and the kids are in 2 different schools and she works days and I work graveyard... Help please!?

After this video I'm a little upset the Honda shop I took my car to for a P0420 couldn't figure it out. Very simple. Thank you.

I just replaced 3 o2 sensors and then I get a p420 code. This is driving me crazy I need a smog

early in the vid, you said that Cat works best at like 12-1600 or whatever, but with the test on the good CAT, it was nowhere near that. ?????

eric, thx for sharing man. your vids are very informative and its wonderful that youre volunteering your hard earned time to allow others to save money and DIY:) idk about your subaru but i do know atleast in the older vehicles that you can obtain an eastern brand converter for about 50 ( my volvo 240 is around 39 give or take) universal. how good are the eastern ones though at that price id think shit but fill me in on this because if they are any reputable quality ill just replace my original instead of welding the spots that are leaking on the body.

I just got this code on my Toyota corolla 2001 I don't know much about cars and I don't have the funds to be able to pay someone else to do it your technique is awesome. my car has been idling rough for some time now I just didn't know how to fix it and then today my engine light came on I'm really hoping its not the converter and its just the o2 sensor sure a lot cheaper.

Wait. So basically the cat is useless? Just an emissions thing? Doesn't affect the engine or its productivity? Am I wrong in this because that's basically the first two minutes of his vid.

Eric, I think you've over simplified what cat converter actually do. Old two-way cats didn't even do a thing to NOx emissions. Nowdays caltalytic converters are a "three-way" type because they perform 3 functions: -Burn unburned fuel (hydrocarbons) to CO2 and H2O (consumes oxygen) -Burn CO to CO2 (again consumes oxygen) -Reduce NOx to N and O2 (releases oxygen) O2 sensors are used to keep the correct ratio of oxygen in exhaust to keep all those 3 reaction going.

Hi, I'd just like to throw something out there, for comment. I own a 2006 Cadillac DTS, w/130K miles. Started getting P0420 codes, a few K miles ago, would set code at between 15-30 miles intervals! Action I took to correct this PROBLEM. #1.Started using " NO ETHENAL " Premium gas .#2.Started using Archoil AR6200, gas treatment . After a few, tanks of gas /Treatment, I stopped setting the P0420 code. Last code set , 300 miles ago ! Cost of gas is high, but worries down! P.S. I also use Archoil AR9100, in engine oil. FYI, I figured this is in the ( general) O2 senser/ catalytic converter area ! I know a lot of worry stopped when it stopped setting the P0420 cade .

we don't have emissions here and the guy I go to for inspections will take a 6 pack of mickeys to look the other way on things that don't involve vehicle safety so I just run with a test pipe on vehicles that have had cats go bad

Those damn subaru's always have bad cats because they burn oil :\

Very informative video but I have a question. What if the scan tool reads the O2s operating normal but the inlet temp of the cat is 150 degrees warmer then outlet? I'm trying to diagnose my car with your method and this is what I'm finding.

We don't have any of those emissions tests in my part of TN either. They used to in Nashville (Central TN) but not sure if they still do. At any rate, I am still glad the car I am restoring does not have any of that nonsense on it. The vapor recovery system is enough to fool with. I do plan to monitor my EGT at cyl. 1 and 8, along with cylinder head temp but not sure if the Edelbrock heads I'll be using allow the latter to be done easily.

Damn wish I had one of those tools to plug into my car I kno my converter is shot