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In this video I show you how I like to identify a failing or failed catalytic converter and then verify the repair once I am finished. -Enjoy!
How Catalytic Converters Work: https://auto.howstuffworks.com/catalytic-converter.htm
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50 thoughts on “P0420 p0430 catalyst efficiency below threshold – testing verification”
  1. Avataaar/Circle Created with python_avatars Sambo and the masonator says:

    2004prius running rich what do I do

  2. Avataaar/Circle Created with python_avatars Mike Hog A Nator says:

    I have an 02' Blazer zr2 4.3, no codes, check engine light, etc. One day it just lost power bad! Hard shifting, high revs, etc. I honestly thought it was my new HD Tranny I had installed (4L80E)
    But, the Cat was plugged! 3 mechanic shops with $5k scanning tools couldn't figure it out! Stupid..
    I took it to a recommended shop & that Ole mechanic knew immediately what it was. Changed it out with a $120 high flow Flowmaster Cat & 300 miles later?
    My Check engine light came on last week. P0420- "Bank 1 Temp Below Threshold." Changed the 02 Sensor & the light w/ Same code came back on! Bought the #2 02 Sensor & just installed that 1.
    It's always ran damn great. Even with this code. You can't tell it's running at a red light with the AC on.
    I did check with a scan tool & everything is showing correctly. Fuel trims, bank 1 & 2 02 Sensors. So we'll see. The only issue was, I was getting 7mpg!! However, she runs great & fuel trims showed good when I was getting 7mpg. I was getting 14mpg. I'm doing more idling out back on my ranch than I do on the highway. So that could be 1 reason my fuel mileage is crap. No harsh fuel smells from tail pipe. Clean as can be.

  3. Avataaar/Circle Created with python_avatars Mohammed Akram says:

    But my Question is, If Bank 1 is fine, Why it should throw the error P0420, Since this code is related to Bank 1

  4. Avataaar/Circle Created with python_avatars Mechanicsville804 says:

    Thank you!
    John 3:16
    For God so loved the world that he gave his only begotten Son that whosoever believeth in Him shall not perish but have everlasting life.

  5. Avataaar/Circle Created with python_avatars 2 Ol' Vets says:

    Hope maybe you an give me an idea on this situation. 08 Altima 2.5L b1s1 shows 2.275v and has little movement. b1s2 .69v pretty steady with the graph all over the place. It’s as if the graph is reversed on what it shows for the 2 sensors.
    The scan toll is fine checked it’s function on our 5.3L with readings that are normal an the graph show the way it should.
    Any ideas?

  6. Avataaar/Circle Created with python_avatars Patrick Ramsey says:

    Hello great video
    I have a 2010 Jeep Grand Cherokee with a PO 430 threshold bank 2
    Any would be grateful

  7. Avataaar/Circle Created with python_avatars Sachs Gs250 says:

    What is upstream?
    What is downstream?

  8. Avataaar/Circle Created with python_avatars Gary R says:

    Eatin antifreeze and oil like it was its job… Lol. Good one 😂

  9. Avataaar/Circle Created with python_avatars mike says:

    It's so cool when you find documentation as to the criteria for setting the 420 code. It really made this video worth watching twice. Great job. I bet Mrs. O had to look it up. Lol

  10. Avataaar/Circle Created with python_avatars mike says:

    Got coated with ka ka

  11. Avataaar/Circle Created with python_avatars Hola! james waugh says:

    Great knowledge

  12. Avataaar/Circle Created with python_avatars soundsaboutright says:

    I have a 2008 tahoe ltz flex 5.3 po430 code it all started po420 430 running to rich before I did spark plugs the check engine would flash sometimes with stability control light then go off. Be good for a couple days then come up.but after spark plugs no flashing just stays on for po430. Did all o2 sensors too. The couple times before it would come on then flash..it was like a loss of power almost could hit the gas down and wouldn't wanna go anywhere but then would all of a sudden jump back to reality and start going. Idk what to try to do next. I also sometimes feel like when I refuel it will act up idk if a fuel pump could do anything like this.

  13. Avataaar/Circle Created with python_avatars Jay Dahl says:

    I would think that there could be some useful synergy working with other smart techs in a bigger garage, but you prefer to work alone? One of the things we all seem to have learned from the Covid pandemic is how much we need to be with other people. Or maybe with the internet you feel like you're never really working alone? Be careful though, working alone in a shop can be dangerous. In the garage where I work OSHA requires at least two techs in the garage before we can do any work (or so I am told by the boss). Whatever the case, take care – you produce some very interesting content, and you're an asset to the entire auto repair industry. Thumbs up.

  14. Avataaar/Circle Created with python_avatars Ron Wilson, Bus Driver says:

    Would leaks in the exhaust cause a p0420 code? Or just a bad catalytic converter? Or both?? The first time it popped up was when I hit a bump and the code came on. I think that is what caused it.

  15. Avataaar/Circle Created with python_avatars Bonnie James says:

    We don't have emissions in OH no more …. Casper keeps taking those cats and hiding em……!!!😂🤣😂🤣
    And I heard when you do replace them you should stay O.E M. But then someone said walker an magnaflow work for replacing being close to O.E.M. shit already need an exhaust with that an 4 cats ………I'm dead…☠☠☠☠☠☠☠
    With Labor..,,,, like 2400$
    I didn't even pay that for the car…..🤔🤔🤔🤔🤔🤔🤔🤔

  16. Avataaar/Circle Created with python_avatars Scott Venor says:

    Question Eric. I'm not a mechanic but love working on cars. Hey great channel. My question is I have an 06 Altima and my service soon light comes on intermittently and then miraculously resets. I ohm'd out my upstream O2 sensor heater and read 2.3omhs. Ok I think. The shield on the upstream is slightly ripped and I know for a 5 wire o2 sensor this is the reference for the sensor. Would be wise to replace both o2 sensors. Car has 318K. Probably should just replace. Thanks

  17. Avataaar/Circle Created with python_avatars The Next Hobby says:

    What I'm learning is that while there are things that can cause premature failure of a converter, once you get a P0420 or P0430, there really isn't much to confirm or verify about its health.

  18. Avataaar/Circle Created with python_avatars Brio 31 says:

    Hello
    So after a year you still have a good repair done
    Your O2 sensors still ok
    No other problem found on your car ?

  19. Avataaar/Circle Created with python_avatars mrau92me says:

    From where did you get the new cats?

  20. Avataaar/Circle Created with python_avatars Aaron Grabowski says:

    Stoichiometric is just so much fun to say!!!

  21. Avataaar/Circle Created with python_avatars TheBigTizzie says:

    Got this code on my Jeep GC. How much $$$$ was this repair?

  22. Avataaar/Circle Created with python_avatars Angelo Reese says:

    I have a 2011 xc 60 Volvo and Iam getting a Po171, po174- po430 code . Would like your opinion on it, thanks.

  23. Avataaar/Circle Created with python_avatars ddh says:

    What no fix it in a can for cats.

  24. Avataaar/Circle Created with python_avatars sam bitar says:

    sir, direct explanation to the point well explained thanks

  25. Avataaar/Circle Created with python_avatars الكاتب ALKTAB says:

    HHHHHH Thank you )::-

  26. Avataaar/Circle Created with python_avatars Paula Jones says:

    So true, overheating kills the cats quickly. Some makes (especially Subaru) are disgustingly prone to frying cats from misfiring. Don't ignore misfires. With a blinking CEL for a misfire, your instinct may be to put your foot to the floor to attempt a rev tune-up . Big mistake, you're just adding more raw fuel to the hot fire. By the time you find a safe place to pull over and shut down the engine, it's probably too late, cat(s) already fried. It only takes one of these episodes especially when more than one cylinder is misfiring. The blinking CEL light is a good indicator things are going to get expensive if you ignore it.

  27. Avataaar/Circle Created with python_avatars Edgar Maldonado says:

    Hey Eric, firstly I'm a huge fan of yours. You are the perfect example of a true mechanic.
    Secondly, my son has a 2003 Honda Accord EX and there were no check engine lights on.. The intake manifold house was cracked so I replaced. The next day the check engine light came on and the code is p0430. I don't know if I messed up the hose putting it on cuz I was rough, but can a intake manifold hose be a reason for the code p0430 coming on or is it a coincidence?

  28. Avataaar/Circle Created with python_avatars Odane Barnett says:

    I like your video mane Whoo Haaa 👍🙂

  29. Avataaar/Circle Created with python_avatars Mavic Aerials says:

    I changed my Cat and I can't get the Catalytic Monitor to complete test. It continues to show Incomplete. I've driven over 125 miles now. What driving tricks do I need to do to get it to complete the test?

  30. Avataaar/Circle Created with python_avatars justice incognito says:

    Blah blah blah. Just shut up and do it

  31. Avataaar/Circle Created with python_avatars Itamar Guiracocha says:

    You are the best
    I have a 2009 Honda Accord V6 3.5
    I have to codes pO420 p0430
    Why 2 at he same time
    Any suggestions
    Thank you

  32. Avataaar/Circle Created with python_avatars Shaggy Rogers says:

    My upstream sensor (AFR/O2 sensor) doesn't work completely. No o2 data on mine except on air fuel ratio. Sensor 2 (downstream) works. Can malfunctioning AFR cause P0420 code? I replaced all my exhaust and cat and downstream but haven't done upstream yet.

  33. Avataaar/Circle Created with python_avatars SDCarAudio says:

    excellent diagnosing. I just aquired a Jeep Liberty 3.7 with p0430 and everybody else threw 02 sensors at me to replace. Didnt fix it.

  34. Avataaar/Circle Created with python_avatars DarK Toad One says:

    I bought a used 2013 GMC Sierra from a young kid and started having trouble and the thing was throwing 5 codes at me, ending up being intake manifold, exhaust leaks and cats, all I could see was big dollar signs. A week later a friend of mine who works for a tow service brought in a totaled 2016 Silverado with only 17,000 miles on it. I got the two cats and stock exhaust for $200!!! It's not what you know but who you know sometimes, I was so lucky.

  35. Avataaar/Circle Created with python_avatars NoahWL says:

    Thank you so much for this video! This is THE best explanation I have ever seen or read on how a catalytic converter affects O2 sensor readings. I've had a vague understanding for a while but I feel very confident reading O2 sensor data now.

  36. Avataaar/Circle Created with python_avatars tra the handyman chicago says:

    20014 chevy traverse 95,000 miles two cats replaced broke down soon after thats when i took over took i through all scheduled maitenace that had been left undone over the years , i took intakes off the valve covers off i was blameing the pcv system which is inside the rear valve cover dont beleive that change the pcv valve bs , you have to clean the inside of that rear valve cover a.k.a the pcv valve hive , it was full of sludge the real pcv valve is the rear valve cover so changing that little whistle aint gonna do diddly . that why its so hard to get out . i recommend people should take the valve cover with the pcv vale on it completely off gas soak it
    you weould believe how much shieat builds up in there .

  37. Avataaar/Circle Created with python_avatars Alexis DeVille says:

    The precious metals are Platinum, palladium, and rhodium!

  38. Avataaar/Circle Created with python_avatars burny knob says:

    hey would manifold leak cause this fault?

  39. Avataaar/Circle Created with python_avatars Primo Paradero says:

    I appreciate your presentation and explanations. I have a 2004 Toyota Sienna with a P0430. I am gathering various insights from explanations. Yours helped me a lot.

  40. Avataaar/Circle Created with python_avatars joesnowmobiles says:

    Love your stuff! Question on a 2012 Acadia, had a friend replace his bank 1 cat and 02 sensors but still getting code P0420. I'm thinking maybe timing is off, is there a way to check that? No other codes showing. FYI I dont think the proper diagnostic tests were done before this work was completed.

  41. Avataaar/Circle Created with python_avatars justaworkin says:

    I really appreciate you making these videos. I have watched a ton of them just for general learning and this one is specific to what my truck is doing. It's nice too see how you go out of your way to fully verify the problem instead of just throwing some parts at it and hoping it works. You also show us and explain the diagnostic process so that we can know what we are looking at. The comedy side is a huge bonus. Thank you sir. Now I can go dig into my truck

  42. Avataaar/Circle Created with python_avatars New York Traveler says:

    I have a 430 and a 455 code

  43. Avataaar/Circle Created with python_avatars springfield45 says:

    So, how did the original cat get ruined…. ahh heard it at the end, heads replaced for oil consumption.

  44. Avataaar/Circle Created with python_avatars Derek Chung says:

    Eric, if the upstream is air fuel ratio sensor, there is not fluctuation up and down, we can never tell if cat is bad?

  45. Avataaar/Circle Created with python_avatars dwoodog says:

    well I've watched enough of these car repair channels to realize you either buy a scan tool or a parts canon.