Diagnosing a catalyst efficiency code (P0420 or P0430)

Uh oh, it’s the dreaded P0420 (or P0430)… This Ford Taurus gave me the opportunity to discuss catalytic converter testing, as well as a chance to demonstrate an oxygen storage test. There’s a lot of misinformation in the industry about converter efficiency codes, and I’m hoping to clear up a lot of that with this case study. To be clear, this video is addressing catalyst efficiency codes ONLY, not restricted exhaust problems!
Engine Performance Diagnostics chapter 5 pages 24 - 27
Symptoms
check engine light (P0420, P1000, P1270)
Fix
replaced the failed catalytic converters
Tests shown
understanding the significance of the P1000 code and how to inform your customer
understanding how catalyst temperature is important to catalytic converter diagnostics
using exhaust gas to heat catalysts for testing purposes
checking for other potential faults such as faulty O2’s and exhaust leaks
performing an oxygen storage test using propane enrichment
using a scope to view multiple O2 sensor signals
how O2 signals can look good but still fail a catalyst monitor
detecting a borderline catalytic converter
checking for external sources of catalyst failure, such as misfires and fuel trim issues
understanding the distinction between a plugged catalyst and an inefficient catalyst
Tools used
Autel MS905 MaxiSys Mini Diagnostic System with Connector Kit - USA Version
www.jbtoolsale...
OTC 7148 Propane Enrichment Kit
www.jbtoolsale...
PicoScope 4425 4 Channel Standard Diagnostic Kit
www.aeswave.com...
Playlist
(Chapters 4 and 5) Fuel Trim and Oxygen Sensor Testing
• (Chapters 4 and 5) Fue...
Related videos
O2 sensor testing (fixed lean) P0174, P0154, P0155 - Mitsubishi
• O2 sensor testing (fix...
P0133 O2 Slow Response (reversed O2 connectors) - Hyundai
• P0133 O2 Slow Response...
How to test an oxygen sensor on a Honda (scope vs voltmeter)
• How to test an oxygen ...
Downstream Fuel Trim (A James Danner video review)
• Downstream Fuel Trim (...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdan... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC 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 ScannerDanner LLC, 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 ScannerDanner LLC.

[@mhiggins3460]

Finally, someone who knows what the hell they’re talking about. This video is a true diamond in the rough. So much BS associated with the P0420 code. Thanks a ton for taking the time to make a quality, informed video

[@ScannerDanner]

Thanks so much!

[@micahrobles5210]

Seriously. This video clears up so much of the mystery in regards to Cat inefficiency DTCs. It makes sense now why the spark plug extensions hack works to temporarily trick the ECM into thinking the cat is fine. Pulling the sensor out of the stream and reducing the amount of gas it's exposed to emulates the lower O2 value the ECM is expecting. Note to nerds like ScannerDanner, be sure to tell the hillbilly why it works so we can limit the amount of backwoods magic they push. JK... Nice content!

[@johnharbour633]

​@@ScannerDannernew to the concept of scopes... possible explain how you choose to connect leads?

[@ScannerDanner]

@@johnharbour633 a lap scope is nothing more than a very fast voltmeter, you would connect a scope to get a signal the exact way you would connect a voltmeter to get a signal. One lead to the wire you are testing and the other lead to battery ground

[@davidkeyes2435]

@@ScannerDanner I really need you me help telling me if this means when it jumps (usually) is it clogged or just failing?? Like if it is still flowing it has no effect on performance so it doesn’t mTter to me but if it’s clogged that is performance issues???

[@twistedimaginationballoons9641]

I've watched alot videos the last few days, working to making sure the cat is my issue. Even bought an "entry" level scan tool. This is by the far the best explained and informative video I've found. Thanks for helping a handy guy like me, play mechanic when I have to. 🙄

[@ronaldmahoney1283]

You are an expert in teaching theology step by step so that anyone could fully understand the concepts of automotive to do most any repair given the aptitude of the individual! I totally commend you for that! Thank You!

[@ScannerDanner]

Thank you Ronald

[@NIS_ONE]

Well I ran into this today. Wife's car throwing a p0420 (2011 Nissan Altima S 2.5) Checked for leaks, checked sensors, checked fuel trims, and honestly I was a little lost. Then I got and idea💡 search for some scanner danner p0420 trouble shooting videos, came across this one which just stepped my game up when it comes to confirming a bad cat. Ran a propane enrichment test BINGO bad cat. Man I love these videos. Before I can say and admit I was a parts changer but now I have learned the error of my ways watching many MANY of these videos by Mr. Danner. Thanks again for all the great you do my good sir!

[@ScannerDanner]

Thanks so much!

[@JBAutomotive794]

Paul, I can't tell you how many times I've learned something from your videos over the many years ive been watching. Thank you so much for taking the time to make these videos. These are priceless for new techs showing them the theory of how modern vehicles work. Cheers brother 🍻

[@ScannerDanner]

Thanks man. Some of the material is timeless and is just as relevant today. Appreciate your comments

[@2secondslater]

Been binge watching your videos again. We had huge problems here in Oz with the Holden Commodore (US Pontiac GTO I think), with the early LS series engines throwing P0420 and P0430 codes, GM Holden must have made hundreds of thousands of dollars, if not millions on replacement convertors, which, came with replacement exhaust flange gaskets. After the first two or three I saw with the fault I decided to do a bit more testing, smoke tested the exhaust, with engine not running, no leaks, smoke tested the engine whilst turning it over by hand, exhaust pipes plugged, no leaks. Finally flooded the engine running with the smoke tester, with UV dye added to the smoke oil. I discovered UV dye staining around the donut style flange gaskets, the leak would only occur with the engine running, the problem was the gaskets would go hard with age and then leak when engine vibration was a factor. GM Holden made a massive amount of money selling new convertors when the fix really was the new gaskets that came with the new convertors. After the initial testing we made hundreds of fixes to customer's vehicles by replacing gaskets only. Moral of the story... test, don't guess.

[@DanWallis86]

Hey Jake. Great write up. I’m in Australia too and see these codes quite often. Very interesting. Where in Australia are you?

[@2secondslater]

@@DanWallis86 Perth mate

[@DanWallis86]

Me too. Are you on Facebook? Can I send you a message on there?

[@2secondslater]

@@DanWallis86 not on FB.

[@DanWallis86]

@@2secondslater no worries. I like your write up you did on the exhaust leak. Thinking outside the box a bit. I’m in a few mechanic groups on Facebook and a mate of mine has a shop in gnangara. We have been trying to organise a couple of training nights for local mechanics to learn about pulse sensors and scope use. Would be good to get people who like to take a somewhat different approach to repairs rather than just firing the parts cannon.

[@Leroyjenkinsjnr]

Awesome video. I've got a vehicle coming in this afternoon. An MOT station has told him his car has only just passed emissions and he needs a cat. I cannot wait to test it now! Thankyou

[@SaltyTubers]

Six and half years later, still relevant and helpful! Thank you @ScannerDanner!

[@steadyeddie7453]

One difference now is that many upstream sensors are air fuel rato (AF) sensors which produce different graph readings. So comparing waveforms from an upstream sensor to a downstream sensor doesnt work. The point being be sure if you are dealing with an upstream O2 or AF sensor. The emissions sticker under the hood will tell you.

[@MarkBlack-e5z]

Just realized this is 11 years old and still 💯 relevant! Awesome video to run across after an hour of data stream readings on all 4 sensors while driving etc to look into the p0430 I am having intermittently. This video is gold! I'll be confident moving forward now. Especially after the propane test! Thanks.

[@ScannerDanner]

I'm glad it could help you out. Thank you so much! And I agree, it is just a relevant today!

[@3rdbass618]

Excellent Sir! I bought my 2006 Chrysler 300 in 2005. Check engine light came on within a month. It ran rough for a while and eventually started back running like a sewing machine, as it does today, still. The light stayed on though. I kept procasting and failed to take it back to dealer for repair while under warranty. When you said a converter can be bad while a car runs smooth, it made perfect sense, especially since the reputable car repair shop replaced OEM oxygen sensors after the p0240 code came up, showing they needed replaced. The light is back on after 53 miles with the same stored (not active code) I am now convinced that the converter is bad and will by one from the dealer and have it installed. I hope this will take of the problem once and for all.

[@mike-yp1uk]

I absolutely appreciate your dedication to create better technicians. It's time to sign up and get saturated by all your material again. It really makes all the difference. I made major strides in my career as a result of using this advanced training.

[@ScannerDanner]

Thank you Mike! Looking forward to hearing from you in the comments section of the classes

[@desiefiautoelectrician7150]

There is a lot to learn in each of your videos. You are a good person. You share your experience with us.

[@sizzlacalunji]

This is gold. I have been struggling with my accord and trying to understand these things and this made it so easy. Will download that ebook. That’s a price to pay to learn and understand what’s going on vs spending hundreds to a mechanic who will do trial and error and still have the code...

[@ScannerDanner]

Trial and error certainly is not the troubleshooting I teach. Thank you very much!

[@_valles3438]

Thank you for the graphics showing the results of both the good and bad catalytic converter oxygen sensor readings!!

[@UnknownMexicanMuslim]

Any other UTI Technician learning more from this channel than the classes ever taught 😂

[@klmachineandwelding4834]

Fantastic video. Helped me tremendously to diagnose a P0420 code to make certain that the converter was actually bad. Thanks for a really informative video.

[@ozzstars_cars]

Ughhh the dreaded P0420. My wifes 2001 Subaru Outback, 3.0L six cylinder, 190K miles started to throw this code now and again for several months. Well tuned engine, no exhaust or intake leaks. Engine was running good. I removed and thoroughly cleaned the inside of the original PVC valve and added a high quality fuel injection cleaner in the gas tank. I cleared the code. It has been 6 months now, NO problem. Most 420 codes do mean a cat replacement is necessary but not always. Great video!

[@thereckchanic4709]

Well said, I would do the same especially after checking for any leaks on the intake and exhaust. Sometime just cleaning the sensor or replacing it will do the truck. I’ve heard of many guys replacing the Cats and still had the same results.

[@U.B.A_AutoDiag]

@ScannerDanner this is exactly how a study videos supposed to be.i am only beginner and your channel is a store of knowledge i follow, watching and studying. please, accept my appreciation for a job you doing here. thank you and best of luck.🤝

[@ScannerDanner]

Thank you! This is an example of one of hundreds of classes i offer just like this on my website www.scannerdanner.com/join-scannerdanner-premium.html Hope to see you there!

[@U.B.A_AutoDiag]

@@ScannerDanner I would love to.. But before that have to finish to watch all your videos here )))) Cheers

[@ScannerDanner]

@@U.B.A_AutoDiag for sure! And we have over 900 videos here on KZbin and over 600 on my website. I mentioned the website because it contains ALL of my classroom lectures (like this one), where here on KZbin I've only sampled from them from time to time. Anyway, no matter where you watch, I appreciate the support!

[@NavyGirlO6]

Thanks, Paul! Fantastic education on what we can look at to understand cat status. Diagnostics over parts cannon. Because of this vid I found ForScan available for my ‘05 Ford Escape 3.0L, and well worth the price of a dedicated OBDII connector with Ethernet cable. I can now evaluate these same values and graphs, which has alleviated my concern about the front two cats (had to replace the rear, which crapped out not long after repairing the famous Ford Escape ignition coil problem causing misfires). So much more confident in monitoring things myself now.

[@user-up3xc1np4g]

I have a 2001 taurus it was throwing the PO420 code as well, plus gas mileage was down. Changed all 4 O2 sensors. Dumped a bottle of cat cleaning solution in it at 1/4 tank drove like 45 minutes. Cleared codes. And the PO420 code popped back up. Got online and googled the PO420 codes it said check O2 sensors which I replaced all 4, check ECS (engine coolant sensor) sensor. I scanned it it was running at 174 going highway speed until I slowed down then it would go up to 185-190. So I decided to change the ECS sensor to see what it would do after clearing the codes again. And the PO420 code hasn't popped up since then and the temp has been at 185-190 since and my gas mileage went back up too. And it's been a week since changing the ECS sensor. So I'm guessing it was ECS all along with the PO420 code and not the cat's or the O2 sensors. Thank god I didn't replace my cat's w/o changing my ECS sensor first. I do cheap parts first b4 going to the most expensive parts. Sorry for the long story lol.

[@scottykilmer3920]

i had a car with a p0420 code diagnosing. It wasnt the cat or oxygen sensors, but the problem was a faulty intermittent crankshaft sensor !

[@blueocean9305]

You’re no parts chaser. Well explained and thoughtful. Thanks.

[@confidential8738]

Wish i lived in PA. I could probably pass ur class jus from the amount of time spent the last 8 months on ur videos. As always. Thanx again man

[@spoke2soon]

Extremely thorough, and I am grateful for it! Thank you for enriching my troubleshooting tactics.

[@Dark_Knight_USA]

Greetings: Use VIN tag not other tags...true. Sometimes there is a midyear production change. Use the later designation. Good show. Thx 4 the share.

[@joshuagibson2520]

Thanks man. Most valuable video there is on the topic. Wish I'd watched it first. The shorter vids I watched taught me just enough to be dangerous. You really went over a lot of variables that are important. Thorough as can be. Thanks again.

[@ScannerDanner]

Thank you!

[@ScannerDanner]

It will depend on the com protocol as well as the scanner used and how many data PIDS you are displaying at once. So it is not set and cannot be relied upon for a time base. Unless you has a run time data pid to compare next to and some cars do provide that PID

[@TheR35nismo]

very informative video, love the content, successfully help me to determine which o2 sensor was failing on my car and also help me save some money, thanks mate

[@BlueEyeTableRockLake]

Great info, My friends 2011 Arcadia has po420&30 codes still with all new o2s and cats. When I heard it wasn't fixed I scanned the SUV and found the downstream o2s almost mirror the upstream sensors. He said they put in OEM parts.??? Now I've got some direction to go after S & L trims all looked good. It runs great and no other values out of range. O2s all respond correctly to rich lean commands. I'll check common components to both banks like PVC, leaks intake or exhaust, and them run the o2 retention test. Thanks! Oh forgot GM TSB PIP5232A states check engine block grounds on vehicles 2015 and older if you have cat failures. I find that interesting.

[@ScannerDanner]

Did they use OEM cats? I doubt it as they're 3 or 4 times the cost of aftermarket. Unfortunately that is what is needed on these! Factory cats only!

[@mauriceupton1474]

Thanks SD you have one of the most informative channels on KZbin !

[@jjones9290]

How goes it Scanner Danner! Just wanna say thanks so much for taking the time, initiative and having the care to make and post these videos! I have been working on a car with all the symptoms this one had and just learning to read scan tools and the graphs on one and I'm hooked! I have never looked at computer diagnostics this way and frankly I'm fascinated now and want to learn all I can bout them! I'm almost certain at this point given my data and after seeing this video( not to mention the chunk of ceramic honeycomb that blew out tailpipe on test drive[good thing I stopped to see what noise was])I most definitely have bad cats and probably caused from dead O2. I'm headed over to your website now! Please keep up your channel and fine job thus far! You're a fantastic teacher!

[@malisa696]

I like this video. I had some issues with troubleshooting catalytic converters. With my scanner I can see in frame data oxygen sensors mV and buy looking them I determine is the catalytic converter good or bad, but I can not be 100% sure. I do not have graph mode so I am relining on numbers I see. Now, I will do more measurements with scope as in this video. It is very important to tell to the customer in 100% that converter is good or bad...not just to assuming.Great video Paul.Thanks so much.

[@whitehistorymonth3563]

This is one of the best videos I've seen on KZbin. Now. I just need money for an expensive scan tool. I bought the $44 one now. I'm like damn it.

[@Jake-me4ze]

Harbor freight $75 Zurich zr8

[@christopherbarone3602]

Great info used this info to fix bad cat on 05 Ford Taurus had down stream o2 stuck lean watched video again and found the bad sensor thanks Mr danner

[@BigEightiesNewWave]

Gold Standard stuff here, bookmarked, notes taken and saved.

[@johnferguson7235]

How much propane are you introducing? Do you just keep injecting more propane until the short term fuel trims respond with a full rich signal? You are the master of the scanner; love to watch you work. You capture the info on the video quite well. The extra effort shows.

[@antor.j.medrano]

i love how informative this video was, I already knew this but i wanted to super make sure this how it actually works.

[@abdallahmohamedgelwah736]

Really it's the best and perfect explanation i have ever seen,,,, thanks man ,,,translate this quote and mention the speaker ( الهندسة كما يجب ان تكون )

[@alanmatthews5949]

Wished you did bonus footage of the propane test after repair.

[@johnnysprocketz]

The most brilliant mind to ever do the dam thing, the brother too is impressive. Would give anything to be a fly in the wall at that shop for a day.

[@nathanielmoore5677]

Best explanation video for cat efficiency codes I’ve seen. I’m getting good oxygen sensor behavior but yet throwing cat below threshold codes on both banks with brand new cats…I can’t bring myself to risk it and throw factory cats in if it’s not going to solve the problem 😬😬 2007 tahoe 5.3

[@ScannerDanner]

Factory cats unfortunately my friend

[@ScannerDanner]

Or an anti-fouler in the rear O2s 🤫

[@nathanielmoore5677]

@@ScannerDanner I put them in both rears today haha we will see 🤞🤞

[@GoogleAccount-ii9sj]

@@nathanielmoore5677 did it work?

[@ScannerDanner]

Thanks for the reminder about Mode 6. I rarely use it and should more often

[@stage3performance]

I just finished section 4 & 5 in your book so this video was posted just in time! Thanks Paul

[@vsboost]

Hey Paul, Great video, i just fixed a P0420 on a 4cyl Barina, turned out the cat was blocked up (full of carbon deposits), the car LTFT was at -30% and the car was bogging down on load, in this instance i did only a back pressure test to give me direction, i will try using this method if i get the chance.

[@eric63377]

Good write-up/ video.. And customers wonder why they are paying 120 per hr + to diag their car.... Also I had a 2018 suburban I installed an aftermarket cat on and it threw code as well for it.. rechecked data and it wasn't enough oxygen storage.. so I installed a FACTORY GM cat and all was good after that...

[@Dark_Knight_USA]

Greetings: Based on the data provided I tend 2 agree with the final diagnosis and customer advise. Thx 4 the share.

[@Dwohman]

Thank you for the info, it helped me read my maxicom mk808. Now I know what I'm looking at.

[@jkdatlvnv]

As has been mentioned by ScannerDanner, 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 offering 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

[@PhilArttz]

Thank you for this video, I finally understand how the sensor values work and what they mean. Now I can diagnose my sisters P0420 ^~^

[@sirsweetness8332]

I think you are an expert! You are humble. 😊

[@mikenelson3102]

I cant remember who or where i picked this up from, but emission systems now a days (unsure of when "now a days" started) have the ability to randomly try and set CAT codes by adding fuel and waiting to see proper response from downstream O2's. O2 spacers is what i suppose emission standards are trying to make obsolete.

[@mofeedfouad7391]

That's was a GREAT DETAILED INFORMATION ... Big thanks

[@Charkatak]

Very informative video! Few days prior to watching this video, my friend asked me to look at his 2015 Ford Explorer(ex Police Interceptor) with 92k miles. My knowledge about cars is limited and this video made it obvious :) Basically his car showed a check engine light. The code with got was P0420 which seemed to be Bank 1. I told him that the code means something is wrong with the way catalytic converter is working. I looked at the live data and marked 4 oxygen sensors and fuel trim data to see the graph. With my limited tool, I did notice that one of the oxygen sensors was marked red and was fluctuating a lot. From your video I now understand that upstream sensors should/will fluctuate, but downstream should usually be less active(when at operating temp). Also his STFT is at least 22%+ or more, but LTFT is at 0%. 1) So this P0420 code always means downstream reading is not efficient enough? 2) You think Cat is the issue here?

[@Wes_5kyph1]

All I'm getting on an '09 2.4L Toyo Camry is this lone P0420 code. Sensors were all replaced a 2 months before the CEL even came on. Going to try some fuel additives, maybe even inject water/ammonia to steam clean. Too bad located an exhaust leak isn't as easy as finding an intake leak.

[@Rdenaro]

Thank you so much for this Paul. Looks like I need to keep some propane on hand for my next P0420/P0430 codes. This appears to be a narrow band system? Would same principles apply for vehicle with a wide band upstream system the reports in mA and a downstream reporting in mV? Data PID’s may look a little different but the oxygen storage test principles remain the same.

[@JoelAutomotiveInaction]

nice video it support you eBook cat testing chart, Paul what test method will be better to apply when I have a/f sensor on upstream? , at this point I can not compare upstream and down stream , thank you very much for this upload.

[@jamesvdl3583]

You are right about using a factory cat. I was talking to a sales rep for an aftermarket cat company and they told me that their cats did not flow the same airflow as the factory's flow.

[@ScannerDanner]

IT is not a flow thing. It is a precious metal thing. The factory cats are using either more of those metals or different types that are more effective. There is a reason that aftermarket cats are not worth much to a salvage yard compared to a factory one.

[@richschaff5504]

run scanner for 60 seconds and determine how many frames elapsed. Divide 60 by the number of frames. The result is secs/frame.

[@HighestRank]

How about just watch as it puts the live frame numbers on the screen? Looks like it marked every other frame.

[@debtfreehouse6216]

A very knowledgable teacher, thanks

[@therealspixycat]

May be combine the up/down o2 and stft/ltft? The ecu can trim the very low stft very rapidly when you cut off the gas?

[@mlb0611]

I have solved many issues with reflashes, including Cat codes, all they are doing is raising the threshold for tripping a 420/430 codes on those reflashes

[@autohublibya2870]

Great effort, and greater information. Thank you a million for your time.

[@joemasterman4305]

I have been gathering O2 storage numbers off known good cars lately, I am seeing 2-4 seconds on average as well.

[@jaygames1980]

This brings more light to my old schooling.

[@knobrush]

06 Dakota 4.7L v8. last august(about 130k miles) I replaced the cats/y-pipe and all four O2 sensors. Check engine light came on yesterday. P0420.

[@ScannerDanner]

Aftermarket cats are junk. You're lucky you got a year. I've seen them flag a 420 after 2 months. Make sure there are no exhaust leaks before pricing a factory cat

[@knobrush]

@@ScannerDanner No leaks right now. But interestingly all the Dodge parts sites show "discontinued" but they're still available through Mitsubishi parts sites. 52013780AB

[@geoffschulz]

Excellent information! Very thorough, very useful!

[@mikewithers7685]

during your tests the o2s22 seemed to be lean at 200mv. thought at or around idle should be around 400 to 600 mv ??? is this normal ?? or what should the o2s2 read. thanks Paul for great videos !

[@shawnbroman]

Awesome & dialed in diagnosis tutorial 🤟

[@ScannerDanner]

I don't plan on making any major changes. some additional hyperlinks added for quick reference to my youtube videos maybe. but these can be found in my playlists I have recently created for each Section in my book. So you are good to go with the paper version if you like. Any brand new material, say a new chapter on GDI would NOT be added to either the eBook or paper book. It would be separate. (We are talking a few years away from now before that happens, I need my own case studies first)

[@leemassey9065]

Awesome video..I've got a 2008 Dodge Challenger SRT 8 that keeps throwing a check engine light. First it just came on, and this last time the check Engine light was blinking off and on and the car was running very rough. So I took it back to the dealership. They said they replaced all 4 O-2 sensors. They drove it, and it came back on. Same code as begore. It said Fuel trim issue, lean bank 1. They are telling me that the computer is reading the codes like the catalytic converters aren't working up to Federal standards for emmissions. Needless to say, they've had my car for two weeks and can't figure it out. Do you have any idea what it could be?

[@ScannerDanner]

@@leemassey9065 a blinking light is a misfire code and rough running suggests a misfire too, it is not the cats, take it to someone who know how to troubleshoot

[@carlthome6004]

Excellent. More 'tools' available in the bag. Nice job.

[@r.weaver3769]

Mine shows P0420 and P0326. 2007 Hyundai Entourage, 205k miles. engine reportedly was replaced @ 38k. The only time the downstream mimics upstream is after idling for several minutes, bring RPM to 2k readings normal, and remain after return to idle. after about 7 to 10 minutes symptoms begin to reappear. Am about to attempt propane test using lab scope, have not tested KS, yet.

[@Dr650rob]

I have a 420 and 430 and bad mpg on 3.5 ecoboost. Do you think it's fuel injectors or hpfp the cats only seem to be a year old

[@IMFDB]

GM's newer vehicle have way higher standards for monitors converters. They use 49 known working converter samples saved in the ecm and compare it to the actual suspected bad converter. I've seen the rear 02 sensors not fluctuate and p0420 still sets. People that commit emissions fraud by modifying the rear 02 sensor to fool the ecm are probably the cause of these high standards on new vehicles make it difficult to diagnose and requires a lot of brain power and reverse engineering the techs may not get fully compensated for.

[@TheMagican614]

customvideo454 why do you think so many techs just throw parts at vehicles. Because if they don’t they won’t make any money!

[@Jonathan-us4ig]

I prefer to monitor the issue the same way the PCM monitors the issue. Watching sensors on a propane enrichment test is perfect. Checking cat temps gives you an idea if the cats are alive, but won't give the same in depth answer as reading the signals from the PCM.

[@Jason607]

I love these videos and have learned some things about them. Nice to see someone who actually test and not just read the code and guess. I have a question about one aspect. I have often had cars come in with cat inefficiency codes but if I see other engine issues such as EGR, MAF, MAP, upstream O2's, misfires, or vaccumm leaks and I usually fix those first and clear it out and let it go and see if P0420-P0430 comes back. My question is will a good cat show that it is inefficient with other running problems or is it safe to say that cat is on the edge of failing anyways? I don't want to diagnose something to be a problem if it's really not but then I don't want to temporarily fix something just to give the owner a headache down the road.

[@ScannerDanner]

I handle those the exact same way Jason. Especially O2 related faults.

[@MRMAN-wb1tv]

*I replaced THE COMPLETE exhaust system on my 04 gs300, and the 4 O2 Sensors, but one sensor Bank 1 upstream threw a code, and it was simply an exhaust leak from bolts backing out*

[@grumblesaw4415]

Hey in this video you show the custom configuration screen on the snap on unit, for the life of me i cant find the st Fuel trim. Also what does the MNTR (HO2S1) B1), stand for? Both HO2S1 MNTR (B1)AND H02S2 MNTR (B1) show lean. 2006 xtrail 2.5lt. great video

[@dandearman2871]

I just bought a 2018 GMC Sierra with 17500 miles. It wasn't a day later I had a check engine light and the engine was running rough. I took it to the dealer and when they test drove it they got stranded and had to get towed back to the garage. Ended up the fuel pump died on them and they replaced it. I picked it up in the morning a few days later and that night got another check engine light. Took it back the next day and when they checked, it had the cat efficiency codes. They replaced all of the catalytic converters and the down stream oxygen sensors. The story I got was this truck was part of fleet the oil well guys used and they may have let the truck run out of gas and maybe that damaged the fuel pump? What could they have done to damage the catalytic converters?

[@mrthomson5582]

hi, iv got a head bursting problem with my emissions my bank 1 s1 is reading normal compare to videos iv now seen but it's the bank 1 sensor 2 the numbers are matching the upstream!? iv no codes on scanner or no engine management light on!? hoping it's just this 02 sensor and not cat ! iv ran cataclean through it and retest is Wednesday, any of your professional thoughts would be appreciated?

[@joey1917]

Thank you for the video is very helpful, can you tell me what was the root cause that made the CAT go bad ?

[@ScannerDanner]

so many things! Misfiring, fuel imbalance issues, oil burning over a long period of time. Anything that makes the cat overheat will kill it. It sort of smooths out all the little nooks and crannies that catch and store oxygen. Then when it gets too hot, it will melt all of that together and become a restriction. Also, contamination can occur from all sorts of things from the fuel being burned to the oil being burned. In theory, they should never "go bad", but they do. Sometimes there is not a cause that you are going to fix. In fact, in most circumstances, that is the case. As long as your fuel trim numbers are good and you have no misfiring and no driveability problems, change the cat and you'll be good for another 150K. But NEVER use aftermarket cats!! Factory only, unless you want your P0420 code coming back in 2 months.

[@thatsubae]

Great stuff man, that propane test is on point 👌🏼

[@SS-zl3go]

Nice video. Just a reminder the cheap infrared thermometers use a "cone shaped" view form the front of the instrument. The further away you are, the larger the sample area. The laser that they use is a little misleading. Its meant to be a guide only, and is NOT the actual point that's sampled. Evidence of this is true as your readings were fluctuating all over the place and its unlikely the temperatures were that different within a half inch of pipe. It was probably seeing the difference between the surface temps of the pipe and heat shield. Anyway, for purposes of catalytic testing, its a good tool and you did show the concept well. Just don't use the temps as absolute because these instruments have their limits, especially ones w/lasers that suggest a pinpoint reading.

[@johnferguson7235]

+Eric “ss195” G You can drill a small hole in the exhaust pipe and place a thermometer directly into the exhaust both upstream and downstream of the CAT

[@wingman358]

another great video, very informative. you're one of the best. thanks Scanner Danner!

[@HighestRank]

He's already denied being a god.

[@wesleybrabant3595]

Everyone know Scanner Danner. Great video Dan.

[@hayguey7952]

Will the water moisture coming out the back exhaust count as a good cat.because cats turn carbon deoxide into water right.

[@advancedleveldiagnostics]

Great info, Thanks for all your videos, I feel like I'm always learning something new from your videos! Does service info ever give a time frame for the oxygen storage test?

[@ScannerDanner]

not that I am aware of my friend

[@sivucit]

Very Nice.. Paul. You always stand outstanding..

[@BigEightiesNewWave]

4:46 Is idling in driveway shortly after my Focus went CL enough time to be considered a "hot cat"? I'm guessing not. Have no codes, and my scanner is rudimentary compared to here, but I can see cat-monitoring O2 looking like the middle part of the red DS graph, then it gets closer to .45 volts but isn't totally flat. It says US and DS switching is OK, (under component tests) but says HO2S11 Voltage amplitude fail I.D. 11 Module $10 test value 0 Minimum limit .50 Is this anything to be concerned with? Again NO CODES.

[@ScannerDanner]

No sir. Cat is definitely not hot until you're driving it. Although some more modern systems have fuel/timing strategies with a cold engine for the sole purpose of heating the cat

[@Loyalvic89]

Awesome! I just had a car (same make and model as this one,) in the shop with the same code. I did the same upstream/downstream O2 comparison and found on bank one the frequency and amplitude were identical. I also did the inlet and outlet temp test and it really wasn't conclusive like you said it wasn't. I didn't know about the oxygen storage test, thanks so much for another test to put in my repertoire!

[@derekkchung]

If the upstream is an air fuel sensor, the downstream O2 sensor will never fluctuate, right? Troubleshooting that would be a whole different ball game?

[@abcdefgh9138]

Great video, as usual! My experience agrees with yours; it's not uncommon to have a low-mileage vehicle with no running issues and bad cats. Have you had any cases of cat codes that were solved with a software reflash? I.e false cat code that didn't return after applying an update that addresses such issues. Thanks!

[@dieseldog2457]

Hey Dan, good video thanks. I get the p0420 code often on Subaru's in NZ, this video is helpful. What differences would you get using a gas analyser when doing this test? when doing MOT tests back in Scotland we did a catalyst stability test, we found any faulty cat would read high on co. We also found any running issue would show high hydrocarbon level. If all else showed good but lambda was out the most likely thing was up stream o2 sensor. What are your thoughts on this? Thanks

[@HotRod-wv4vm]

Excellent explanation on catalytic converters 👌

[@mr.technician2638]

Sir Paul,,,good day..can I ask also a question? I saw on a 2016 gmc yukon or on impala 2016 their is a 3rd catalytic converter...but no oxygen sensor attached from it. What is the purpose of that sir? I try to search on service information but there's no info. Hope you will answer me this question also sir thank you sir Paul

[@hitmonRay]

how do i tell if a sensor needs to be replaced or if the cat needs to be replaced?

[@rickbauza]

HI PAUL.PAUL THIS IS IRRELEVANT TO THIS VIDEO, JUST NEEDED YOUR INPUT. I HAVE A 2003 CHRYSLER VOYAGER 3.3 VIN R.AM HAVING ISSUES WITH THE COOLING FAN MY DIAGNOSIS HEAD TOWARD THE COOLING FAN CONTROL MODULE.I WAS TOLD AFTER REPLACING THE COOLING SYSTEM CONTROL MODULE I NEED TO FLAFH THE P.C.M IS THIS TRUE ON THIS VEHICLE.WILL HIGHLY APPRECIATE YOUR HELP THANK YOU PAUL GREAT LEARNING VIDEOS THANKS FOR SHARING THEM WITH US FELLOW TECHNICIANS THANKS AGAIN RICK BAUZA.

[@ScannerDanner]

Thank you Michael for your input.

[@islamsh.4862]

Why voltage dropped down while rpm is high and steady in bank2 O2S2 and vice versa?

[@spinroyd]

what is the cross count over .45v that triggers the code. the ecm is programmed to count the crossovers of the rear 02 sensor. Isnt this part of Smog analysis. All car manufactures have the threshold. What is it?

[@gueroburban4989]

Ihad the po420 and po430 I changed my cats and upstream 02 sensor and my downstream I used the original ones? You think my downstream sensors are bad? And not sending in fo to my upstream??

[@MAISTROPERFORMANCE]

Hey Paul, what of valve do you have at the end of your propane bottle? I tried doing the oxygen retention test, but I was not successful due to the fact that I was using a soldering torch to feed the propane into the intake, but it never got the engine to run off of the propane. Please share where you got it or tell me if I did something wrong. Thank you.