ccorogers

The codes my 96LS are giving are 0420,0430 both banks, called a few shops, everyone says call Lexus so i did. Lexus of Shreveport was my choice, and got a really nice lady on the phone kathy i think, she looked on the MAGIC LEXUS computer and she said the fuel may be running too lean, but wasnt for sure, said it definately isnt the catalytic converters, (thankfully) and she suggested i start by replacing the front 02 sensors, as they do the important reading for the ECM and the rears are only due to federal law? I have no idea. the CEL has been on for about 45 days and I took a trip to Bourbon Street this past week. that is a story for another website!! The light was on the entire time, some on the freeway i got upwards of 100mph, after leaving New Orleans, the CEL wasnt on. I looked and thought ok...... thats weird, but was confident it would come on again, and after about 30-40 minutes it did. I just want the light out, and by the way the car is running like a beast, like a Lexus with a V8. the gas milage was about 21 mpg. any takers???

PureDrifter

iTrader: (10)

take it to any competent independant mechanic and have them check for exhaust leaks first.....

most common cause of P0430/P0420.

LEXTEK1

OK well, P0420 and P0430 are catalyst inefficiency codes period! The sub O2's are responsible for monitoring the catalyst. The sub O2 circuit needs to be checked for sure but I am afraid you have bad cats. However nice the girl was she is clueless on your problem. If the exhaust was leaking to the point the sub O2's were not functioning you would certainly know it! The sub O2 circuit should be checked for waveforms. Without the right equipment however, I concur with PureDrifter. You need a competent Independent or Dealer to check it.

PureDrifter

iTrader: (10)

lol? if this is the case i would have had bad cats for the past 3 years and still pass cali smog.

my cycle:
-replace cat-x pipe gaskets
-drive 500mi (scraping around driveways the whole while, my exhaust is one piece and tends to shift a tiny bit breaking the seal on the gaskets eventually.)
-get CEL (p0430 or p0420)
-replace cat-x pipe gaskets and reset CEL
-drive 200mi, get smogged, pass.

catalytic inefficiency refers to many things, last of which is the cat.

LEXTEK1

This is from the Toyota TIS system. I dont know of too many other problems you can have between the front O2 and the rear O2 but a catalyst. Please explain the many other things it could be besides the catalyst? I need the education!


CIRCUIT DESCRIPTION
The ECM compares the waveform of the oxygen sensor located before the catalyst with the waveform of the oxygen sensor located after the catalyst to determine whether or not catalyst performance has deteriorated.
Air-fuel ratio feedback compensation keeps the waveform of the oxygen sensor before the catalyst repeatedly changing back and forth from rich to lean.
If the catalyst is functioning normally, the waveform of the oxygen sensor after the catalyst switches back and forth between rich and lean much more slowly than the waveform of the oxygen sensor before the catalyst.
But when both waveforms change at a similar rate, it indicates that catalyst performance has deteriorated.

(1) Connect LEXUS hand-held tester to DLC3, or connect probe of oscilloscope between terminals OXL1, OXL2, OXR1, OXR2 and E1 of ECM.
(2) Start engine and warm it up with all accessories switched OFF until water temperature is stable.
(3) Race engine at 2,500 3,000 rpm for about 3 minutes.
(4) After confirming that waveforms of heated oxygen sensors bank 1, 2 sensor 1 (OXL1, OXR2), oscillate around 0.5 V during feedback to ECM, check waveform of heated oxygen sensors bank 1, 2 sensor 2 (OXL2, OXR2).

HINT: If there is a malfunction in system, waveform of heated oxygen sensors bank 1, 2 sensor 2 (OXL2, OXR2) is almost same as that of heated oxygen sensors bank 1, 2 sensor 1 (OXL1, OXR1) as shown.

There are some cases where, even though a malfunction exists, MIL may either light up or not light up.

dashan

I had the same code in my 96. The code was gone after I replaced post-cat O2 sensor.

LEXTEK1

Yes, thats why we check the waveforms before we replace a very expensive cat. Your code would have been a P0420 or P0430, depending on which side was bad. He has both 420 and 430. The chances of both sub O2's being bad is remote but possible. The reason PureDrifters car passes emissions is the cat efficiency is good enough to pass California emissions tests but does not pass the Lexus test! Replacing the X-pipe gasket, which is way past the cats and the Sub-O2's has no affect on his CEL.

Actually, I'm not sure what he is talking about with an X-pipe. The factory configuration has a front "Y" pipe, a center pipe and rear mufflers. If he has some other configuration, he has something different than you do and I'm not sure how that applies here!

PureDrifter

iTrader: (10)

the xpipe used in my car is part of a complete custom exhaust, was merely used as illustration. the gasket i am talking about is part no. 90917‑06078 which comes right off the cats onto the front of the factory y-pipe (not present in my car) but the leak you may possibly have in your exhaust can be different, and as far back as the center resonator.

lextek-you're a tech, you must realize that the self-check on the LS is pretty sensitive. There's no way that my car would pass a CA sniffer with cats that were in bad enough shape to trigger a CEL since the OBDII emissions readiness monitors would show as incomplete on the smog test (if i had just reset it) and I would fail automatically. The reason i can install some new gaskets, drive it around, then pass is because I just make sure not to scrape my exhaust against anything during the ~100ish mi emissions readiness monitor cycle so as to not develop that stupid minor exhaust leak again and not a single problem.

exhaust leaks are a common cause of catalytic inefficiency codes (specifically the P0430 and P0420), leaks pre and post cats (range is approx from the manifolds themselves to the y-pipe in front of the center res/cat depending on configuration.) would very easily alter O2 sensor waveforms unevenly due to incoming fresh air during reversion pulses (hence i often see my cel trigger when I'm cruising on the fwy at low speed or trolling neighborhoods at night trying to keep my car quiet), triggering the CEL. hunting for exhaust leaks is the simplest thing to do (simpler still if you've got a can of Seafoam or similar product as the smoke will be easily visible) and both easier and cheaper (initially) than trying to diag the O2 sensors with an oscilliscope (since most of us won't have the stupid expensive Toyota/Lexus testers).

3UZFTE

I had a p0430 in my GS430, and it turned out to be the rear o2 sensor on the driver's side stating it was seeing a steady .28v signal. Replaced the o2 sensor, and it fixed my cat inefficiency code. That being said, it did have a slight leak after the cat at the exhaust flange, but not big enough to cause an inefficiency code.

python

iTrader: (4)

http://www.obd-codes.com/p0420

youre a master lexus diag guy? you guys are merely a middleman anymore..u hook the car up to ur diag machine and it sends a signal to a main computer that relays the information back to you on what steps to take to fix the car? or is this done only on the new cars?

LEXTEK1

Yep, you've got the DS position all figured out. But, on the new cars it sends the information straight to your brain via the osmosis oscillator. Geez, just when I was starting to be able to plug in the OBD2 connector without looking, they go and change it all up! Those pesky Japanese engineers....

python

iTrader: (4)

takes all the fun out of it huh?

PureDrifter

iTrader: (10)

i wish OBDII worked like that