My bad. GS300.

 

part #'s for the gs430 were in the FIRST thread he provided.....



but for the to lazy to click members (not meaning you milellie,just saying)

 

I just got the P0420 on my 01 GS430. "it says catalyst system efficiency below threshold bank 1" Should I change ALL the O2 sensors or just the one from bank 1?

 

and for bank 1 which one exactly do I need? the front right or left?

 

I got P0420 after ran over a big rock which pinched the midpipe. Replaced the bad section and both b1s1 and b1s2 sensor still no luck. Lexus specialist point out the bank1 Cat was bad even so the ODB2 reading green on both Cat, good temp and good o2 sensor, but o2b1s2 wave form jumping. While saving money for new Cat ($850 + labor) I replace myself the Megan racing midpipe ($365) then the Cel p0420 never come back for 3 weeks now. Both side b1 and b2 sensor wave form are similar nice and smooth now. So it must be the secondary Cat on the midpipe. P0420 is bank1 but can be either the main Cat or secondary Cat on the passenger side of 2006 lexus Gs300

 

I just purchased new cats. Looking to do full exhaust tune up. Before I go to install all these parts, my mechanic said it be wise now that everything is there to replace all 4 o2 sesnors. My GS430 is about to hit 100k soon. I'm choosing to do that. I also have gotten that PO420 code. It turns on & off. I'm tryna kill the whole problem all at once. New cats, new gaskets, new o2 sensors. I went with Sewell for the cats & gaskets. Here's my dilema now. Should I go with Denso or NTK from Japan for the o2 sensors? I seen the part #s sakataj posted. Very helpful. If anyone is going with NTK o2 sensors, here are the part numbers for 01' GS430:

Pre-Cat Driver Side: NTK Part #24560 ~ $71.03 on eBay SELLER---> autoparts.titan1
Pre-Cat Passenger Side: NTK Part #24564 ~ $75.06 on eBay SELLER---> autoparts.titan1
Post-Cat Both Sides: NTK Part #24605 ~ $74.50 on eBay SELLER---> abcmarts

If anybody has used NTK instead of Denso, can you please post your experience with it. Is it better/worse? I really just wanna make the best decision on the closest thing to Lexus quality without spending the big $$. Also, I hope this serves as good advice on anyone going thru the same scenario. Just get EVERYTHING done at once. I think it'll help better as opposed to fixing a few things at a time. Not everyone got the same money, but try to stick to doing things correctly once so you won't have to do it again.

 

May I ask you how much you paid for the cats? I just need a good laugh! You do know that 95% the problem is just the o2 sensors right? The cats in these cars are built to last forever. There's a reason they cost over $1000. Everyone I know including myself with a p420 code just changed all the o2 sensors and the problem never came back. I highly advise you to return the cats and just do gaskets if you want but mainly just o2 sensors. I'm sure many will agree with me on this one

 

And no it does NOT serve as good advice because if you had done any research you would see most people just had to change the sensors and the ones that changed the cats did them because some stupid dealer or mechanic told them to. You will not find anyone who changed the sensors and then still had the problem so needed the cats. This is NOT an American piece of **** car where cats are involved in a tune up. Most parts on this car are built to last far beyond the standards of most new cars now and days

 

If this is to me I understand bro. I paid the discounted prices off Sewell. I've read plenty on here as well. I made the decision to buy both cats+all gaskets+all screws & bolts to the exhaust+all 4 o2 sensors. Maybe I might've not needed to but I'm thinking longetivity of my investment. IMO, the car has been great to me so I'm just tryna keep it close to 100%. Also, I understand the cats might be built to last but one of my cats had a little crack when I first bought the car. Also, both cats read defective when in the shop, so they say..... I hope it was just the o2 sensors. So if I can salvage any of my cats, I'll help out a fellow CL member in need of one. Either way I was going to intsall it all new on my car anyways. Thanks for the output bro!

 

Just got em in today. Off Sewell Parts. Very happy with quality. Feel confident that everything will be ok when I get repairs in.

 

May I ask how much you paid for those front cats? What's funny is on my car the flange that connects the cat to the manifold is a little bent and allows minor air leak. I would change mine if they weren't expansive but they're supposed to be. I already spent so much on this car.

 

They are expensive. Cats are at least. I ended up paying about $2k just for the cats. But only because I wanted to. Everything else around the exhaust is relatively cheap (gaskets, studs+bolts, etc). I'm almost done with buying all the parts. I'm going with Denso for the 4 o2 sensors. Afew more weeks and my exhaust should be like new. I think I have the same problem. On top of my cat, I have a slight air leak and it makes the car sound like a baby pickup truck ... But I will try my best to get it all fixed correctly. I guess our cars suffer from that. Exhaust leaks + wear and tear of the gaskets. Good luck tho bro. I hope you get it all fixed asap!