joncurry94

I'm getting CEL codes p0420 and p0430 for Cat System Efficiency below threshold bank 1 & 2 respectively. From my understanding this is front driver and passenger. I have seafoamed the car months ago but haven't in a while, so I am assuming I should seafoam and check for potential exhaust leaks first? What else?

Also, I attempted to clear it just for the sake of attempting, comes back almost instantly after I drive it for a few minutes.

jaaa

I had this code recently and it turned out to be an exhaust leak. Right at the flange, just past the cat. I ordered a new gasket, but when I put it in, it still leaked bad. Turned out it was leaking long enough to eat away a small portion of the flange itself. I ended up buying a can of VersaChem muffler weld. It worked great and managed to seal all the leaks and the codes are now gone.

joncurry94

Awesome jaaa, so coming from an inexperienced standpoint, I can put my LS up on ramps and probably spot any leaks easily? Or is this something I am going to have to be pretty mechanically inclined to figure out? Most of what I have figured out thus far has been due to sheer research on the forums.

jaaa

I only had it on bank one and you could hear the difference between the two banks. Then you can use your hands to feel the air escaping(just remember- its HOT!). This isn't rocket science, you could easily do this on jack stands or ramps. If I had to do it over again, I wouldn't even have replaced the gasket. Just used the steel weld to cover up the leaks. And believe me, I had zero experience before I went after these leaks. Feel free to ask any questions you might have. Took about three patches for me to get all the leaks. You hit the biggest ones first, then as the leaks get smaller in size, you can feel just the pin hole leaks. Here is a picture of what I used. If your leak is where mine was, it will be just after the first cat(at the flange) where it meets up with the pipe going to the last cat. I didn't have a leak on the other bank like it seems you might.

joncurry94

Sounds simple enough, I'm going to take a look at it tomorrow and see what I can find. I'm sort of unfamiliar with some of these terms but they sound pretty much common sense. Banks are sides, correct? IE: Driver side passenger side?

jaaa

Yeah, bank A is the drivers side and bank B is passenger side. Just take a good look at the connection point(flange) just past both catalytic converters on both banks.

dicer

And can most likely be a bad cat.

joncurry94

Okay cool, so if sealing doesn't fix the issue, would this be something I should take to a shop to do?

billydpowe

iTrader: (1)

first off, check it out, you can use a piece of vacuum hose, put it by your ear and the other end by the pipe, (it cant burn you that way) and you can hear the leak... and make the decision....

joncurry94

Good idea, I bought some extra vacuum hose when I went to change my transmission fluid, that'll work out well. I am assuming a leak is a very noticeable sound?

jaaa

If you are under the car on your back, you should be able to both hear and feel the leak. Slightly wet your hand and put it an inch from the flange and go up and around it. You should be able to feel the leak as it blows across your hand. It will be right at the seam where the two pipes meet. My worst leak was right at the top where it was harder to tell, but had several others around the seam. I took a picture of the gasket I took out of this flange and you can see how dark it is on top where it had burned the top of the flange as the gasses where escaping: Its on page five of my car post-
https://www.clublexus.com/forums/ls-...w-owner-5.html

billydpowe

iTrader: (1)

yes jon, you will know..

joncurry94

Thanks, after fixing p0763 and resetting the battery after I completed all of the trans work yesterday the code has come back after about 15 minutes of test driving. I hadn't noticed any leaks but I am going to go back and try again one more time. exhaust doesn't sound abnormal to me.

billydpowe

iTrader: (1)

did the po763 come back? or 420&430, or all of them

joncurry94

0420 did come back, 0430 has yet to show up. p0763 is gone and has yet to show up. I am pretty certain following the guide on how to fix the shift solenoid took care of my issue, the part wasn't faulty I checked for continuity. Shifts are so much smoother, too. And I am used to p0763 showing up immediately when i start the car, even after disconnecting the battery or clearing the code, it always comes right back, but it isn't now. How exactly can I determine if it is a bad cat?