Read the message over again. What you want to know is in the graphs for the two O2 sensors and how they track.
Don't worry so much about the ratio itself, worry about how they track.
But you will not figure the problem out just by looking at the plots, you will figure the problem out by thinking about how the emission control system works.
All the time. You take them before it warms up, you take them after it warms up, you take them over the course of driving around. What you are looking for is trends and correlation more than specific values.
Well, that's useless. So you're going to have to plot it on semilog paper by hand. Your scanner does not provide ANY plotting functions?
And the vehicle is long past the age where it should need a new converter.
But that doesn't mean you shouldn't make sure there is no possibility of something else damaging the converter. Because you don't want to swap out the converter and find the problem is fixed but returns.
I know Arlen doesn't want to throw parts at it, but from what I see here, if it's not the cat, then maybe it could be a bad downstream O2 sensor. Those typically aren't very expensive. Even a cat isn't as bad as many think it is. I looked up a cat for a friend's Honda a few years ago, it was ~$300. So, I'd approach it in terms of what do those part costs mean (we know Arlen will DIY), for the future of the car? If it's worth fixing, then I'd go get an O2 sensor, try that first, because you're probably going to want to change that with a new cat anyway.
I'm learning a lot, as I didn't even know the voltage range of the lambda sensors, nor what low versus high voltage meant when I opened this thread.
I appreciate that, so far, you're the only one who posted who knows anything, which I very much admire and hope to learn what you can impart.
As you know, you can't diagnose without understanding, so I've been boning up on how the system works, where I have the same attitude as you do, which is it could be any number of things, but replacing them without first confirming for sure they're definitely bad, is idiotic.
A _lot_ of people fix a lot of things that way; but it's still idiotic. o I see now that a _graph_ is almost essential, for proper diagnosis.
Given the moving nature of a graph, I learned from this video which shows, in real time, what the voltage graph should look like for the rear sensor: o Understanding & Live Graphing of the Rear O2 Sensor #19, by OBD4Everyone
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Given I don't (yet) have a way to graph the results, this video shows how to diagnose using just the live data, which is the redneck way to do it: o P0420 How To Diagnose A Bad Catalytic Converter, by EricTheCarGuy
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Speaking of redneck diagnostics, this video shows how a guy taps into the wires, which I think is too invasive given wire coatings, stainless steel wires, etc., but what's interesting is _how_ he forces a "lean" reading and a "rich" reading out of the oxygen sensor to look at fuel trim reactions: o Test O2 Sensor.mov, by realfixesrealfast
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Literally, he grounds the sensor to simulate lean conditions (to watch the fuel trim respond by adding fuel); and he puts himself as the voltage divider resistor to force the oxygen sensor to output rich conditions.
While his approach (e.g., feeding propane into a vacuum port to simulate rich conditions) is a bit too much for me, we can learn a lot from redneck methods because they distil the problem down to the essential components.
In summary, when I opened this thread, I had no idea what to look for; I still am not sure; but I'm learning to associate low voltage (about ~100mV to about ~300mV) as a lean condition reading - & higher voltage (about ~700mV to ~900mV) as a rich condition - neither of which did I know prior.
I'm also slowly starting to understand that the cat acts sort of like a capacitor for oxygen, where the fluctuations of the leading sensor are damped in the readings of the trailing sensor, such that the rear lambda sensor should be steadier at around a stoichiometric ~500mV even as the front lambda sensor wildly fluctuates between lean & rich.
If that cat capacitor isn't functioning well, then the voltage fluctuations in the leading sensor will be more closely mirrored in the trailing sensor.
A key distinction I need to wrap my head around though, which you seem to have caught upon in the very beginning, is that this is a "warmup" error: o What Does P0421 Mean?
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The keyword here is "warmup" (which only you caught in the initial post). "the Bank 1 Catalytic Converter isn't warming up sufficiently"
This makes the problem harder to diagnose since, as you seem to have realized instantly, it will only show up during the warmup process.
Worse, it happens only "most" of the time, so it's intermittent (i.e., it can go seconds, hours, minutes, or even days between showing up - but it eventually will show up and keep the CEL lit, interestingly, forever).
That's right Arlen, those other people don't know anything and just waste your time. Only one person knows and gives you a hard on. Just rub it now like you usually do
That is the factory method for testing, not "redneck" as you seem to think. As for being invasive, not even close as long as you seal the holes you make or use a backprobe method.
In simple terms it means that the converter isn't starting to operate as fast as the table in the ECM thinks it should given the engines run time, fuel and air states. The ECM looks at the time the engine started, it's loading, coolant temp, air temp, rpm timing, injector flow, air flow and a couple other sensors and using the tables programmed in it has decided the converter isn't starting to do it's job fast enough based on the numbers they used in the programming.
Sometimes this can simply be a bar sensor, IE the rear sensor is sluggish due to contamination or age and the ECM thinks the cat is the issue when it's the sensor. That is the whole point of the graph, you want to see how long it takes on a cold start for the sensors to start working and what the voltage numbers are. The direct testing at the sensor is also the best testing because everything that comes through a scan tool is processed data, it has been known to be wrong multiple times, while direct testing shows the raw data.
Thanks for your advice, as cat "warmup" is the critical parameter for sure!
I agree that the P0421 indicates a catalytic "warmup" fault, where it must be close since I've seen three situations occur multiple times so far: o In most cases, the P0421 is set the instant readiness monitors are full o In other cases, the P0421 is set days after readiness monitors are full o Oddly, once set, it doesn't ever reset (e.g., after 3 good drive cycles)
Of course. o The difficult question to answer is what to test to debug during warmup.
The lambda sensor is heated, so it only takes ~20 seconds to warm up. o But what's expected warmup time for a cat (& how exactly is it measured?)
Yes. Indeed.
I certainly didn't realize this when I originally opened this thread, but I do realize that measuring how long it takes to get to steady state after an overnight rest & morning cold start seems to be a critical diagnostic.
Understood. I'm very familiar with flying leads. o I simply prefer not to do that to other people's cars if I don't have to.
What I need at the moment is to borrow the vehicle and see what I can determine in the first crucial minute. o I know it only takes about ~20 seconds for the sensors to warm up
But I'm not yet sure how to test the time it takes for the cat to warm up. o Especially when it appears to be a borderline condition on this vehicle.
Thanks for that gentle reminder, as I will borrow the vehicle today, but I have to check it in their garage, as I only get one chance a day to test warmup conditions (I think, at least, at Silicon Valley temperatures).
Well, to tell it to you bluntly, I'm not omnipotent. o I didn't know anything when I first posted this thread
I didn't even know the _range_, which I've since learned is basically about ~100 mV for lean conditions, to about ~900mv for rich conditions.
Nor did I know when I opened this thread, what the expected differences were for the upstream versus downstream lambda sensors, where the front should be changing far more frequently than the rear (which should read, as much as possible, a stoichiometric ~450mv under steady warmed load).
What I didn't know at first was why voltages bounced all over the place.
But now I've boned up, a tiny bit, on the fact that the bouncing around of the voltages is "normal", at least for the upstream side, since the engine computer is constantly adjusting the ratio (within seconds) depending on a whole bunch of factors, not the least of which is engine loading.
Further honing what I didn't realize at first is that there are two states:
Steady state (which is where most of my prior measurements lay), &
Warmup state (which is where I need to focus, as you had advised me).
What I need is what most sites don't provide, which is I need to learn more about this warmup process of the cat, since it's a 'warmup efficiency' DTC.
I only get about a minute (or two at most), right?
Yes. But.
I belatedly realized I need to focus specifically on 'warmup efficiency'. o My main focus now revolves around how to diagnose 'warmup efficiency'.
Obviously I need to figure out what 'warmup' even means, which I need to do as my homework, since I'm not even sure how long warmup of the cat lasts (the sensors only take ~20 seconds to warm up, but I'm not sure how long it takes the cat to warm up, nor, if a cat can even warm up twice in the same day given Silicon Valley typical warm nightly & daily temperature ranges).
I'm gonna borrow the vehicle today but it's wet outside so I'm not sure if I'm gonna crawl underneath to check the rear lambda sensor; but I will at least check the live OBD data during the first 20 seconds of the lambda sensor warmup and then the first few minutes, where I'm guessing a cat warms up in, oh, I don't know, within the first five minutes perhaps? o I'll look at an engine temperature reading (coolant perhaps?) o Then I'll look at the front & rear sensors (and what they do over time)
I may need to buy an infrared thermometer to check how the cat warms up in the first five minutes with the vehicle on jack stands; but no sense in doing that until I learn more about how the cat _should_ warm up, as the numbers won't mean anything if they're measured under the wrong sequence.
My OBD scanner _does_ provide plotting functions; but it's second hand (I picked it up at a garage sale for a few bucks). It works fine for live data, but I don't have the cabling or software to view the graphs. o Harbor Freight item #60693 Cen-Tech OBDII/EOBD Deluxe Scanner
It also does 'freeze frame' but I haven't even started to look at what that means to me, in terms of how I can use that to diagnose warmup efficiency.
In summary, I started out with the wrong assumptions, and I ran the wrong tests, and I didn't know how the system worked... but I'm reducing my ignorance by reading up on how the system works, and I'm gonna focus on the all-important warmup process, where I think I only get one chance a day.
Permanent plonk! (the fact such creepy disgusting people exist is scary)
Moving forward, I found this Mitsubishi emissions recall bulletin titled: o Catalytic converter overheating - emissions recall campaign o EMR-05-001REVII, December 2005, Model 2002-05 Lancer
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Purpose: Some affected vehicles have incorrect parameters in the Powertrain Control Module (PCM) software that may cause teh warm-up catalytic converter to overheat and melt when the vehicle is repeatedly driven at wide-open throttle. o For all affected vehicles, reprogram the PCM as described in this bulletin, regardless of the age or mileage of the vehicle. o If an affected vehicle has a Service Engine Soon (SES) lamp on and DTC P0421 set, also replace the warm-up catalytic converter, using an exhaust manifold repair kit.
Affected vehicles:
2002-2005 Lancer models equipped with 2.0L engine.
Customer notification: A letter will be sent to all owners of affected vehicles, telling them to bring their vehicle to a Mitsubishi Motors dealer to have the PCM reprogrammed at no change, and that if their vehicle has a SES lamp on for failure of the warm-up catalytic converter (DTC P0421), they will also receive a new warm-up catalytic converter.
In addition, owners will be advised that the new warranty coverage for the warm-up catalytic converter will be extended from 8 years/80,000 miles to a limit of 8 years/100,000 miles. Until February 28, 2006, replacement of the warm-up catalytic converter will be free of charge, regardless of vehicle mileage.
After February 28, 206, all owners (regardless of vehicle mileage) will be entitled to the PCM reflash free of charge. However, warm-up catalytic converter replacement will not be covered under the warranty if a 2004-2005 model has over 80,000 miles. o P/N MN195802 Lancer 2.0L, 2004, Exhaust Manifold Repair Kit (includes manifold with catalytic converter, gasket, and nuts)
The recall was already performed; but they didn't replace the warmup cat. o All the dealer did was reflash the PCM (i.e., P0421 didn't come up then).
Just in case, this appears to be the $400 + $40 tax recall parts: o P/N MN195802 Lancer 2.0L, 2004, Exhaust Manifold Repair Kit
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"Original equipment genuine Mitsubishi part exhaust manifold / catalytic convertor Fits only 2004 Lancer with 2.0l engine This kit includes the gaskets and hardware for installation. California certified."
I'm not sure yet if there are two cats, but it appears the car may have o A warmup cat, plus, o A regular cat
Since this recall talks only about the "warmup cat" melting due to a poorly coded PCM (which they reflashed, apparently, as per EMR-05-001REVII TSB).
That is if the heater in the O2 sensor is working. The bad O2 sensors I've seen have mostly been for failed heater circuits. But if yours had that I'd expect a code for the heater failure. How old are these O2 sensors? Typical life is ~100K miles from what I've seen. And the code you do have is for warmup period. Sensors are fairly inexpensive.
Clark. County Music Award winner. The guy next to him is Grandpa Jones. Also a CMA winner. Third in line is Gordie Tapp. Far right is Archie Campbell. Youtube disabled comments for some reason.
I like the picture sequence.
I grew up in the late 60s and 70s listening to rock. Dueling banjos interested me for some reason.
Aghast, I happened to use the dejagoogle feature to look at the a.h.r newsgroup, which, much to my chagrin, is more than 99.9% worthless spam. o
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o
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Given the lack of value in a.h.r, I will no longer be posting the results of this thread to that newsgroup, preferring to put the updates on r.a.t which, thankfully, isn't almost 100% worthless spam as a.h.r clearly is.
I'll also drop ca.driving, such that this is the only worthwhile ng: o Request for diagnostic advice to pinpoint least expensive solution to resolve persistent P0421 OBDII DTC
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BTW, the vehicle passed smog today; but that doesn't solve the problem of diagnostics since it only made it through the intermittent window.
THANK YOU for redeeming my opinion of the helpful people on this newsgroup! o
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Clearly a.h.r is 99.99% spam
While I gave up on a.h.r (it's filled with 99.99% spam) with the trollers gleefully ruining the newsgroup for their own perverse childish pleasures, I did just now check the dejagoogle record and saw your post.
Thank you for trying to be purposefully helpful, which is unusual for this newsgroup, as even though who know 'something' (e.g., Clare) are all childish infants in almost everything they claim (Clare should know better, but doesn't - hence nothing Clare says is of any adult value anymore.)
I did find that recall, and yes, it's a Lancer, as I reported already here: o
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I appreciate that you _found_ that recall, as you may have found it before I did (I didn't check the time stamps of our respective posts) - but I wouldn't see _anything_ in just a.h.r because it's worthless to even try to wade through the spams (even my thread was trolled by Ed Pawlowsi's socks).
My thanks to you are for being a good person... purposefully helpful. o Which is almost non existent on this a.h.r newsgroup as it currently is.
I called Mitsubishi who told me the P0421 recall applies to this car, but that the PCM was already reflashed and that they didn't replace the cat, and worse, the recall only applies once (since the P0421 didn't present itself at the time the PCM was reflashed under that P0421 recall).
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In belatedly seeing your message amidst the tons of garbage spam in this now nearly worthless newsgroup, I want to say that I appreciate your help and advice over the years, where you're less frustrated, it seems, by the fact the trolls have taken over (e.g., I tracked Ed Pawlowski's many socks, and they're all easily traced to the same person shown in the sig below).
I will continue to update the thread on r.a.t, where we've already passed inspection but we're working on trying to figure out how best to diagnose a P0421 since it's an interesting problem set which differs greatly from a P0420 in that the P0421 is only a "warmup efficiency" code.
Hence, the only time that a P0421 can be diagnosed, it appears, at least so far given the data I have at hand, is in the first couple of minutes, if even that long.
I know a four-wire lambda sensor heats up in ~20 seconds, but I haven't yet figured out (or found the data) for how long it takes a cat to heat up, where I'm assuming it's single-digit minutes.
That means the only measurements that may likely matter are in the first few minutes, which makes things both easier and harder to diagnose at the same time.
What I did learn though, since I knew nothing at the start, and I still know almost nothing, is that the OBDII heuristics are looking at nine parameters in general, fluctuating the input conditions to see what the output results are during those initial tests of the catalytic converter warmup efficiency.
One or more of those nine tests is showing that the warmup is inefficient. All I have is the OBD scanner with live data & freeze frame.
With that alone, I may never be able to figure out what exactly is the condition that the computers are using to determine lack of warmup efficiency, but I'm still learning, and new questions always arise, e.g. o Once the readiness monitors are set, if you never do a drive cycle, is it possible for a DTC to be triggered?
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If you want, I can apprise you over here in this spam-filled group, when I finally resolve exactly what is causing the warmup efficiency to trigger.
In summary, thanks for being a rare person on this newsgroup who is purposefully helpful, and, I admire how you can wade through the inordinate amount of spam (much of it from Mr. Pawlowski's very many socks, it appears).
On Tue, 17 Nov 2020 23:06:39 -0000 (UTC), Arlen Holder posted for all of us to digest...
Here you go. As always check electrical connections.
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By the way your scanner is not giving you live data that you can can use. You need something more advanced. You don't need the "cheapest" fix-you need the "correct" fix and shooting the parts cannon at it doesn't work.
It sounds like the issue is borderline, IE the cat isn't really dead but under colder temps it takes longer to warm up and sets the code.
The downstream sensor is the one used for this testing, the lambda sensor upstream isn't really involved in the test other than to verify that the mix going into the cat is correct.
Yep, Steady state isn't the real item it tests though, what the test looks for is how long does the cat take to start working and lower the levels going to the downstream sensor.
That is the trick in testing, the easiest way is to use a 5 gas analyzer and watch the numbers as the cat ignites, but not everyone has one. The next is to measure the sensor output directly and see when it actually shows a change. Just remember that it only uses the downstream sensor for this test.
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