Check Engine light - code P0420

I have a '97 Lexus ES300 and got a check engine light 2 days ago. I got it checked and it comes up with a P0420 code. The code description says "Catalyst System Efficiency Below Threshold (Bank 1)".

As I understand, it could be due to a defective catalytic converter, damaged O2 ensors, contamination of converter due to incorrect sealant, fuel, or fuel additive.

I had 2 repairs/services done on my car in the past 6 weeks:

1) I had replaced the flex pipe and the catalytic converter about 6 weeks ago. The flex pipe was leaking and the exhaust was making a lot of noise. My mechanic advised that I also replace the cat. I got the aftermarket (generic) flex pipe and cat.

2) I had a service done a week ago. I got the transmission liquid flushed, radiator coolant flushed and fuel injection service done.

My guess is I am getting this code due to something gone wrong in either of the above 2 repairs/services. The most obvious cause would seem to be the first one, but I don't know if I can rule out the second one as that was the most recent one ( a week ago).

I would appreciate if someone could help me with this. Could the second service cause P0420 to be set? Or is it possible that I just got a bad converter in repair 1? If yes, then would it take upto 6 weeks for the code to be set?

Any additional advice or suggestions would be appreciated.

Thanks, Mark

Reply to
Mark
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I'm only guessing here....

- Could the injection servicing include gasoline additives that may cause "odd" readings in the exhaust gases?

- Is there a harness that should connect to the cat that isn't present in the replacement "generic" cat?

Reply to
Noozer

Reply to
philthy

Reply to
philthy

======== ========

Go BACK to the shop that did the FLUSH's......

explain that the light came on jest after getting the injector flush service and ask them to PULL the codes AGAIN...... AND please CLEAR the codes so you can see IF they come back, or better, how quickly they may comeback. Have them MONITOR the Oxygen sensors DURING a TEST DRIVE!! See if the sensors are reacting quickly, crisply, and changing under various fuel demands. (heavy acell...cruise...decell from cruising speeds)

Make sure they check HISTORY and PENDING codes while they're doing this. These codes, if any, help in the diagnostic process.

IF......the codes reset...or if the shop gives you a bit more info to go on.....do a repost with ALL they're findings and let's take a stab it.

However....if you feel yer lible to be anass to them...git high tempered easy..maybe gonna chewsomeass over they're service that caused yer light to come on..............so that they charge you fer a service that they'de otherwise be more than likely to offer for free to someone that MITE spend more money with them...... then in that case.......

let's guess and save you and them all the heartache aye....

:)

the Fuel System service caused the light to come on.........

the Fuel mixture is now rich...

the injectors were cleaned and now one or more is NOT sealing or the service mucked up either the front or rear sensor on that bank.

jest a guess......

:)

~:~ MarshMonster ~takes a toke......sorts his seeds.......no need in guess'n if next years crop is a good one~ ~:~

Reply to
Marsh Monster

The O2 sensors are monitored closely by the OBDII system and will throw a code if they get sluggish or amplitude/current are out of specs. The most probable cause is a Catalytic converter that is not good enough for a high performance engine. The generic cats may work on a four cylinder engine but fail quickly with a high performance six. Also the second O2 sensor is not always in the right place. A god mechanic with an OBDII tester can analyze the problem and determine where the problem is. This problem also shows up after a blocked EGR problem that prevailed for a period of time.

Reply to
Woody

You don't know that.

It is? Funny, a P0420, is pretty clearly defined.

Nope, got nothing to do with catalytic convertor efficiency.

Not a very good one.

We can expect further brain damage?

Reply to
aarcuda69062

Thanks everyone for your responses. Though I am still confused at this point. I would atleast like to get an idea of whether this is caused by my replacement of flexpipe/cat. converter or the fuel injection service. Without taking any guesses, can somebody point me in the right direction based on their experience? Could a fuel injection service indeed cause the CEL with reason code P0420 - catalytic converter efficiency low?

Reply to
Mark

========== ==========

Scroll up.......read Woody's post carefully..........

The computer puts out the code based on not seeing a large enough difference between the front sensor reading and the rear sensor reading, which is the ONLY way the computer can tell if the gass's are being burnt off by the converter. There in.....the "efficiency" part of the code definition.

The code IS NOT saying.....bad cat..rich exhaust...02 sensor.. or ANYTHING else other than the computer thinks the cat isn't doing it's job BASED on the fact ALONE that the two readings are NOT within specs.

IF.........too much fuel was entering the converter....and the converter is not CAPABLE, for whatever reason, to burn off the excess to a point that lowers the rear reading to within factory parameters for an efficient catalytic activity.....then THAT code WILL set.

IF......the replacement catalyst DID NOT set the code for over

5 WEEKS.......AND..you were putting the same amount of milieage as you always have....on the car...then, for 5 weeks the computer saw the converter able to do it's job.

IF.....you had the fuel system flushed....and the code SET within

3 DAYS........AND..you were putting the SAME amount of mileage on as you always have.......on the car.......then, in 3 days the computer saw THE FAILURE PARAMETERS....... (note the the wording).....had been met to set the code.

NOW.......a DRIVE CYCLE is a factory preprogramed set of variable parameters that MUST be met BEFORE that code will set. I'm not sure, i could look it up, i'm not going to, i don't care, it doesn't really matter at this point.........What the drive cycle for the particuler code is. What does matter, what I do know, what is fact, what the case is...........is that......the car HAS TO BE.......cranked up....warmed up...driven a decent distance... gas pedal mashed and released several times.....brought to a stop....sped back up........gotton hot.....cooled off........and DONE ALL OVER AGAIN SEVERAL TIMES......... BEFORE THE CODE WILL SET. A guess..??.........i'd guess around 3 or 4.........unless you've omitted the fact that you've had the computer codes cleared previously....for whatever reason... :)

so.......IF you drove the car for 5 weeks.......no codes......

then worked on the car.....and then 3 DAYS later....CODES.....

well........yer smart enough to navigate the internet.....i'm shure you can figure it out.

:)

oh........and......one more thing.........GO BACK AND GIT THE FREE SCAN AND TEST DRIVE LIKE I TOLD YOU TOOOOOOOO....

cuz......like WOODY said in HIS post....... a good tech.......will see it QUICK.......

:)

Read Woody's post again...read what he typed. Read my original post.......what i typed.....not what you, or others......think i typed.

anywhooooooo.......... remember......if it wasn't broke before you fixed it, you broke it fix'n it.

fact, not fiction

~:~ marsh ~takes a toke......watch's the readings on the 4gas as he cleans the throttlebody~

Reply to
Marsh Monster

Indeed, you should also.

it's got nothing to do with gass's (sic) being burnt (sic) off by the convertor. It's got everything to do with oxygen storage and nothing more.

Apparently, you were.

Uh, no. the computer 'thinks" that the cat can't store oxygen as it is supposed to.

You really-REALLY need some driveability classes. i.e., why don't cat efficiency codes set when the engine is operated at wide open throttle (rich exhaust)?

His replacement cat was at best 40-45% efficient as installed, and it went down from there as soon as he drove away from whatever lame-brain shop installed it.

Not that I'm an advocate of wallet flushes but, an injector flush using the proper materials should not in any way effect the performance of a properly functioning catalytic convertor.

Actually, it does. It's entirely possible that during the 5 weeks, he never drove the vehicle under conditions that would meet the enable criteria. The industry is full of tales of emissions monitors that won't run even after two months.

Further proving that it's possible that the enable criteria was never met during those 5 weeks.

yeah, a one knee on the ground look at the aftermarket cat.

yup!

Do you even -know- what you typed?

IF it was fixed in the first place.

Workin' on a Sunday so you can someday afford a 5 gas?

Reply to
aarcuda69062

aarcuda69062 wrote in news:nonelson- snipped-for-privacy@news.chi.sbcglobal.net:

It doesn't take long for even somebody not in the industry to find out how a P0420 is set. It is set when the catalytic converter fails the ECM's cat efficiency test.

The test is, from my readings, this: The ECM commands rich for 5 seconds to drain the cat of oxygen. Then it commands lean for five seconds, measuring how long it takes for the secondary sensor to start flip-flopping. If the rear sensor flip-flops too soon, the ECM assumes the cat's unable to store sufficient oxygen, and sets the P0420.

I also understand that there are certain unusual circumstances that can lead to a P0420 even when the cat's fine. These would include air leaks into the exhaust after the primary sensor, or before the secondary. Also, certain Honda models (I know the OP's car is a Toyota) have problems with the igniter electrical connections that can lead to a false P0420.

Reply to
Tegger

The computer looks at the results of the two oxygen sensors, and if the difference is out of range, it throws this code.

This code COULD be because the converter isn't any good, or isn't correct. Or it COULD be because a lot of junk was thrown into the converter briefly (maybe during the injection cleaning) and it couldn't deal with it.

A scan tool that can actually look at the sensor readings will tell you which of these is the case.

Alternately you can just reset the code and see if it comes back. If it comes back, it wasn't due to the injector cleaning.

But right now you don't have enough information to be sure.

--scott

Reply to
Scott Dorsey

So if I reset the code and it comes back, then it is not due to fuel injection cleaning? I could use this approach to eliminate this service and the it would point to maybe a damaged converter?

Reply to
Mark

====== ====== aarcuda69062

Reply to
Marsh Monster

======= ======= On Dec 4, 5:54 pm, Mark >

So if I reset the code and it comes back, then it is not due to fuel injection cleaning? I could use this approach to eliminate this service and the it would point to maybe a damaged converter?

========= =========

What IF....that cleaning busted loose enough crap THROUGHOUT the system and SOME this CRAP is now BAKED on yer sensor/sensors??

but......

you do what you want........

I'VE DONE TOLD YER DUMBASS TO CARRY IT TO THE FLUSH DUDE AND GIT IT LOOKED AT FOR FK'N FREE!!!!!!!!!!!

but........

clear the codes if you want..... then....if the codes comeback...... go blame the dude that put the convertor on.....

jest do this when you do......

make sure you tell HIM.....that system was flushed AFTER the convertor was put on.........i mean........

we do wanna be HONEST here .......rite??

:)

~:~ MarshMonster ~takes a toke.......wonders if anyone here has been smart enough to google this subjest.........takes a toke......lhao~ ~:~

Reply to
Marsh Monster

=============== ================

The flush did it.

there......i said it.......now i feel better.

:)

~:~ marsh ~smokes a big ole hooter.....~ ~:~

Reply to
Marsh Monster

It's not surprising that you wouldn't know this. The answer to the first part is; the atmosphere (duh), which is usually around 21% oxygen but it varies depending on how much dope *you're* smoking in proximity. You know, that air fuel ratio thing. The answer to the second part is; the Cerium wash coat. Like I said, you need some classes because this stuff is (well) over a decade old.

This has nothing to do with whether or not I am smarter than the OE engineers. Oxygen sensors DO NOT react to raw fuel as you implied in your post, the post cat O2 will not set a efficiency code just because an engine is/was over fueled as your post implied.

Speaking of other posts, do you want to take another shot at spelling 'definitely'? (hint; there is no "a")

Well, you posted on Sunday and mentioned that you were watching the "4 gass" while fiddling with the throttle body. So, the real case here is; you felt need for a clever buzz word to lend some credibility to your asinine statements.

So, tell me about your "4 gass", what brand is it? Is it a non-dispersive infra red or flame ionization bench? Does it have constant volume sampling? Does it allow for corrected NOx sampling?

Reply to
aarcuda69062

How about; there would be O2 sensor performance codes setting instead of cat efficiency codes.

Because even though there are thousands of fuel injector flush services done every day, there is yet no industry wide problem with those services causing catalytic convertor failures in spite of the fact that aftermarket convertors are known to be less than

50% efficient (which is no where near good enough) right out of the box?

For trying the cheap way out.

Do these convertors come with a warning that injector flushing is not allowed and/or will void any warranty? (feel free to post a copy)

Why, you're not.

Some of us don't need to because we actually do it every day for a living.

So Mr. Doobie, how many times a day do you use Google to repair your customers vehicles?

Reply to
aarcuda69062

Umm... yes. The fuel injection cleaning isn't doing any permanent damage to anything. It's just dumping a lot of crap out of the tailpipe for a short while.

A damaged (or incorrect) converter is permanent damage.

--scott

Reply to
Scott Dorsey

Thanks everyone for your insights, suggestions and advice. This forum offers a lot of expert advice from different people with different point of views and experiences, and thats what makes it so valuable. I appreciate everyone taking their precious time to respond.

I just wanted to post an update that my check engine light went away this evening. I did not do anything yet. I went to work in the morning and the light was on. When returning from work, I turned on the car and the light was gone. I have made a couple of short trips since then and the light has not come back on. Based on this occurence, I would again have to lean on the experts here to understand what this means, and if it may have temporarily disappeared and could return again.

Another problem that I didn't bring up earlier, as I did not want to divert attention from the CEL problem, was that my fuel mileage had dropped since I had replaced the catalytic converter. Previously I would get about 24mpg and after replacing the converter I am getting around 20mpg. I noticed the drop in mileage after replacing the cat and before the fuel injection service. I have to ask this dumb question, but can the replacement of the cat. converter cause a drop in the mileage too (i.e. if I have a bad cat.) ?

Thanks everyone for your help.

Reply to
Mark

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