Do you expect me to agree with what you just said . . . ?!
If I see an aftermarket cat which isn’t approved for the application, I’m just supposed to pretend I didn’t see it and pass the car, anyways . . . ?!
Perhaps the aftermarket cats you installed aren’t quite efficient enough to prevent P0420 and P0420 from being generated . . .
you might also have other factors affecting oxygen sensor operation, such as exhaust leaks
Why do I mention oxygen sensors, you may be thinking . . . ?
Because P0420 and P0430 are generated when the downstream oxygen sensor is fluctuating at nearly the same rate as the upstream sensor
Since your car seems to be operating well and getting good fuel economy, and you live in a state with no emissions testing . . . I’d be tempted to just leave well enough alone and drive the car with the check engine light staring you in the face
That said . . . don’t assume no new codes are being generated. You could have 20 additional codes, and obviously the light doesn’t change, to reflect additional codes . . .
I don’t know if you plan on ever selling the car or trading it in, but if I were a buyer, I’d low ball anybody selling a car with a check engine light illuminated. It might be a moot point with a 1998 car, though, especially if you’re trading in, because the dealer will only give you chump change for such an old car
Thank you for all that information. db4690
I will do a smoke test on the exhaust system to make sure
there is no leak somewhere in the system.
I did have a small pinpoint leak in Exhaust system several years ago but it was repaired by welding the spot. I guess it is possible a new leak has developed.
I guess this needs to be done before I think of other things.
Do you work in Arizona? No? Then that statement made by bcohen2010 doesn’t apply to you.
Nobody said anything about you ignoring the rules in CA. Many think they are bogus however. Because IF the replacement cat satisfies the programmed requirements of the car by design, it should be satisfactory in use regardless of who made it or what bureaucratic nonsense the company had to meet to register their product…
Come on now, I’m not telling anyone to do anything illegal here. My point is that in most states, you can legally install any aftermarket cat which will fit your car, and result in clean enough emissions to keep the CEL off and/or pass a tailpipe test.
If you own an older car, the difference in price between a “federal” version and a “California approved” version can be $300 or more, and that’s based on Rock Auto prices. Since a professional shop typically charges 2 to 3 times the Rock Auto price for parts that they supply, you can see that this makes a big difference to someone who might not want to sink a $2000+ repair into an old car which isn’t even worth that much.
Today, 8-2-2020 I went to OReilly auto prts and had them read the codes.
He told me there is only one code and that is P0420. No other codes found.
He also said that his reader tells him the code is due to Catalytic Converter defect.
Unless you tell me otherwise, I plan to put a ext spark plug non fouler on the
post Cat oxygen sensor on the side of the defect.
Q. Which Spark plug non fouler is the optimum length for my car 1998 Lexus LS400 ?? I appreciate you all so much. How do I say thank you?
Hi DB4690 thanks
I plan to get a smoke test on the exhaust system this week.
Where is a good place to have a reliable test done.?
I dont know about Lexus dealer. I probably should go somewhere else but where.?
If they find a leak, I’ll post it here.
Here are possible causes:
P0420 LEXUS Possible Causes What does this mean?
Faulty Three-way Catalyst Converter Bank 1
Exhaust Tube
Intake Air Leaks
Faulty Oxygen (O2) Sensor
Faulty Fuel injector(s)
Leaking Fuel Injector (s)
Faulty Spark plugs
Improper Ignition Timing
Faulty Engine Control Module (ECM)
Dirty Air Filter
Texases,
The list is getting a little long for me.
I will check out exh sys leak this week,
I dont think engine has no intake air leaks, I dont hear any abnormal sounds.
the engine runs normal, accelerates normal, The engine operates at normal temp.
as it has in past. I dont think it has faulty or leaky fuel injectors. Last time I checked, 4000mi ago, spark plugs were normal. How do you check for improper ignition timing? The air filter is clean.
Or you could feed the intake a piece of a can of Sea Foam. That will generate some smoke for sure and it’s cheaper than paying for a smoke test. :–)
A few years back some guy at AutoZone fed 2 whole cans into a Ford F250 right in front of the store. Five minutes later he had pretty much smoked out the entire strip mall.
Thanks for that advice,
I’ll park car outside, than close garage door,
Put car up on jack stands
Than put sea foam into intake. start the car
and study the exhaust sys.
Is it harmful to put a rag into tail pipe while I study
exhaust sys from below. or is that unnessary?
Got a new Datsun B210 hatchback with 5-speed manual in 1976. Took it in for the free first oil change. The mechanic bent the throttle cable and it subsequently was sticky at the point where the bend in the inside wire passed the bend in the outside cable sleeve.
I took it back and the service advisor pressed the accelerator and said “That’s the kickdown for the transmission. Nothing needs to be fixed.”
Maybe I missed it with so many comments, but why did you have to replace the cat in the first place? Was the error code the same (P0420)? That alone does not indicate a problem with the cat converter.
Kurt, I took car to only Lexus dealer within 75mi radius and asked for diagnosis for cause of CEL . The answer was I had defective Cat Converter on Right side.
and that the replacement cost would be 2000.00plus. No mention of a code. I assumed the answer was to replace the Cat converter like they suggested. I now know that was probably an error on my part. I probably only need to put a spark plug non fouler on the post cat oxygen sensor on the right side to fix the problem but that is hind sight. I am working on doing that now.
