My check engine light came on and I read the codes, they are PO420 and PO430, the generic OBDII description is "catalyst effeciency below threshold." Any idea on what do I need to do for this?

 

sounds like your post-cat O2 sensors are ratting out your catalylic converters

just like Al Capone, I hate a rat!

this is likely no big deal unless you live in an area that has emissions testing, or if you care about the environment

clear the codes and see if they recur.

 

Thanks for the info. I do not have emission testing here in MN. The car runs fine, the check engine light will go away on its own every now and then but will pop back up shortly thereafter. I will try clearing it with my scanner to see if that gets rid of it longer.

 

if you're slammed and scrape, or even if you aren't/don't, go check your exhaust for exhaust leaks before the rear O2 sensor.

the 0430/0420 codes sometimes prevent the car from going into closed loop so it's not the greatest thing for fuel economy (will make the car run richer than it already does).

Commonly the leak occurs at the lower flange from the catalytic converters to the y-pipe but pinhole leaks above and below this point, but usually before the secondary O2 sensors, have been reported.

source: been there, done that, multiple LS'

 

i bought my 95 when it had only w/ 112k, three years ago . The previous owner took it to the dealer. The CEL light was on and the dealer wanted 4k to replace cats. He decided to sell the car cheap.

This is ghetto but it works.... It was only supposed to be temporary....

I took some aluminum foil and folded it thick around the flange, and put a large hose clamp on it. Reset the CEL light. Hasn't been back since!

car has 148k now and no exaust leaks!

 

Thanks, I'll check for leaks, I know they make exhaust tape too.

Where exactly are you referring to though...

 

can you put the car up in the air either on a hoist or jack stands?
if you can, do so so all 4 wheels are off the ground and the car is supported on frame rails.

have a friend with you to help.

start the car and climb underneath

have a good visual and look for a bent or broken O2 sensor and or wires to the sensor as far up as you can trace them back.

WITHOUT touching any of the exhaust pipes, cup your hand around the pipes and flanges before and after the cat. if there is a leak you should be able to feel it as well as hear it.
if there is a leak, address this first as that could be all you need to do to solve the problem.

if you find no leaks and the sensors look fine from the outside, remove the downstream sensors(with the car off) from the pipe using a 22mm or 7/8th wrench. if they feel like they do not want to crack free, don't force them without having replacements standing by.
once removed, give the sensor tip a good visual inspection and compare to one of the many online resources about fouled O2 Sensors. replace if needed.

keep in mind, O2 sensors are considered a "wear" part and should be replaced every 40-60k miles or 80-100k kms.

Also, Catalysts only last about 8 or so years in normal service. if your car has high mileage or is 10+y/o, there is a good chance the cats are on their last legs as far as being able to clean up your emissions. Magnaflow makes direct fit replacement cats or you can simply have them removed for a test pipe and source an O2 Simulator installed into the downstream sensor which tricks the ECU into thinking the cat is still there and fully functional.

any decent exhaust shop should be able to make you test pipes for about $150, O2 Simulators can be found for as little as $5 and as much as $50 if they are plug and play.

let us know what you find.

 

usually it's that second gasket fromt he cat to the y-pipe, but it could be either.

 

I went under the car yesterday and didn't feel anything but I only had a couple minutes of free time. I'll see if I can get more time today. Anyways, the car is not dropped and it is a 98 with 135k on it.

Just so I know where to start looking, are you referring to here PD?


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car is throwing the same codes. Looked under the car and it doesn't seem to have an exhaust leak before the secondary cats, but it does have a leak towards the back. Where i think the resonators are, before the muffler. Can that cause it too?

 

this is unnecessary and possibly even dangerous


BETTER WAY:

go to your local muffler shop (who you should be sending business to, when you can)

they are quite happy to put your car in the air, and check for leaks, and unlike most other types of mechanics, they will let you walk underneath your car with them during the inspection

I have done this like 100 times in my life, a huge time and work saver, and a pro is helping you find any leaks for free! (you can even tip them!)

 

not every shop lets customers under the car or even on the shop floor, just like not every exhaust shop will simply let you use a bay to find out where your exhaust leaks, if any, are coming from free of charge.
I'm not really sure why you want to or need to send business to your local muffler shop anyways...
The ones around here are less than reputable and nothing is ever for free...

also, if you have a modicum of common sense and are not an utter klutz, checking it out yourself is no less dangerous than changing a tire.

 

I had the same problem on my 99. No leaks, needed cats.

Check out my thread for more info.

https://www.clublexus.com/forums/ls4...r-lessons.html

 

to repeat -

ALL muffler shops I have ever been to will happily raise your car up and inspect your car for leaks for free and let you under the car while they do it - I have done this at over 100 muffler shops across America

It is how they get their business, they locate the leaks, show them to you as they find them, and then give you an estimate and most people have it fixed on the spot - but some of us, go home and fix it ourselves - and I have never found a crooked independent muffler shop yet - it's a little known mechanic's secret!

 

Wow, interesting. I didn't find any leaks either so I was thinking it is the cats. So if you just have straight pipes welded in then I assume I'd still throw codes? I'm not in an emission testing state.