P0420 & P0430 Help please
Listen and read this very carefully to me bro. This is a relatively INEXPENSIVE repair if you just read my advice CAREFULLY. I had this SAME problem for almost 2 years before I changed it. Yes, I ended up buying new cats but ONLY because I wanted to. These cars are equipped with very durable cats. Half the time when they tell you its the cats , it isn't..... OK so this is what I did...
Go to www.sewellparts.com and sign up using your CL account information.
Look for all the gaskets to your car. Before AND after the cats. You will need to replace all the gaskets pre and post cat locations. You might want to buy double of each. Incase your manifolds have deteriorated where they meet that cats , put double gaskets there to insure extra seal. I did. It worked out marvelous. Also, I strongly recommend only buying OEM Lexus gaskets. WHICH IS WHY I SAID SIGN UP AT SEWELL PARTS , 100% TOYOTA OEM PARTS FOR LOW PRICES.
Lastly purchase all o2 sensors. Don't just change one. Change them all the first time. Get the whole problem out the way. I have a GS430 so I have 4 o2 sensors. Idk how many a GS300 has... Maybe 1 or 2. Pre and post cat sensors. Look up on eBay the Denso o2 sensors for your car. You'll be able to get them real cheap. I went with Denso. Good brand.
In total, all your looking to do is replace out all gaskets pre and post the catalytic converters. Also, replace o2 sensors. When there is air leaks, especially IF YOU CAN HEAR THEM, it most likely rotted gaskets before and after the gaskets. The codes your saying that your having all pertain to everything I told you. If done properly, all gaskets replaced should eliminate all air leak sounds and rough sounds from the exhaust. And new o2 sensors will be the icing on the cake. Better fuel mileage. The computer will read new sensors. All that good stuff. Should CLEAR CODES COMPLETELY IF INSTALLED PROPERLY. Hope this helped! I was in your predicament a few months back. I spent lots of money! But because I wanted new cats. Aside from that, when I looked at my old ones they were still in decent condition. I could've cleared the issue with just the gaskets and o2 sensors. Good luck! Try this inexpensive solution BEFORE resulting to new cats. Save your money and do it right at first and everything will come out fine. Have patience!
Go to www.sewellparts.com and sign up using your CL account information.
Look for all the gaskets to your car. Before AND after the cats. You will need to replace all the gaskets pre and post cat locations. You might want to buy double of each. Incase your manifolds have deteriorated where they meet that cats , put double gaskets there to insure extra seal. I did. It worked out marvelous. Also, I strongly recommend only buying OEM Lexus gaskets. WHICH IS WHY I SAID SIGN UP AT SEWELL PARTS , 100% TOYOTA OEM PARTS FOR LOW PRICES.
Lastly purchase all o2 sensors. Don't just change one. Change them all the first time. Get the whole problem out the way. I have a GS430 so I have 4 o2 sensors. Idk how many a GS300 has... Maybe 1 or 2. Pre and post cat sensors. Look up on eBay the Denso o2 sensors for your car. You'll be able to get them real cheap. I went with Denso. Good brand.
In total, all your looking to do is replace out all gaskets pre and post the catalytic converters. Also, replace o2 sensors. When there is air leaks, especially IF YOU CAN HEAR THEM, it most likely rotted gaskets before and after the gaskets. The codes your saying that your having all pertain to everything I told you. If done properly, all gaskets replaced should eliminate all air leak sounds and rough sounds from the exhaust. And new o2 sensors will be the icing on the cake. Better fuel mileage. The computer will read new sensors. All that good stuff. Should CLEAR CODES COMPLETELY IF INSTALLED PROPERLY. Hope this helped! I was in your predicament a few months back. I spent lots of money! But because I wanted new cats. Aside from that, when I looked at my old ones they were still in decent condition. I could've cleared the issue with just the gaskets and o2 sensors. Good luck! Try this inexpensive solution BEFORE resulting to new cats. Save your money and do it right at first and everything will come out fine. Have patience!
Lexus Test Driver
Joined: Feb 2012
Posts: 1,158
Likes: 23
From: PA
Well I have some good news. This morning I installed the manifold gaskets and the 2 donut gaskets, cleared the codes and drove it over 100 miles with no check engine light!!!! So I took it to get inspected and it passed!! So I am good to go!
Thanks so much ANEIDIAZ! Total cost was about $50.00 for the gaskets from lexus.
Thanks so much ANEIDIAZ! Total cost was about $50.00 for the gaskets from lexus.
Lexus Test Driver
Joined: Feb 2012
Posts: 1,158
Likes: 23
From: PA
Lexus Test Driver
Joined: Feb 2012
Posts: 1,158
Likes: 23
From: PA
I'm not quite SURE which one out is exactly but this is it... Remember I have a 01' GS430. These are the gaskets for THAT model. I hope this helps you. And everyone too. Sorry guys. I'm on here rarely. I be working so much.
Lexus Test Driver
Joined: Feb 2012
Posts: 1,158
Likes: 23
From: PA
Well I have some good news. This morning I installed the manifold gaskets and the 2 donut gaskets, cleared the codes and drove it over 100 miles with no check engine light!!!! So I took it to get inspected and it passed!! So I am good to go!
Thanks so much ANEIDIAZ! Total cost was about $50.00 for the gaskets from lexus.
Thanks so much ANEIDIAZ! Total cost was about $50.00 for the gaskets from lexus.
Moral of this post TO ANYONE reading this... Yes I changed out my gaskets and o2 sensors. If your lights by chance turn back on after replacing the gaskets ONLY go ahead and replace ALL your o2 sensors. Wether you got 4 (GS430) or 2 (GS300)... IDK HOW MANY SENSORS THE GS300 GOT... So don't take that number accurately. I know mine has 4. Also IMPORTANT REMINDER when getting o2 sensors swapped out PLEASE AND I STRESS THIS HEAVILY tell the technician who's doing the job PERSONALLY to be careful and be very FRAGILE when dealing with the wiring harnesses to the o2 sensors. They can rip and make the repair more costly.. If you just tell them in the beginning and keep that in they're mind they'll be careful working with your car. Before you get any repairs check on a diagnostic CEL tool that ALL your o2 sensors are reading... That'll tell you if your having a wiring issue or not. AND EVEN STILL they can be reading temperatures but that doesn't mean the o2s are not going bad. It's good to replace ALL AT ONCE.
I hope this experience I've carefully shared with all you guys serves as a reminder and guide to this famous PO430 and PO420 codes. It's not at all complicated if you KNOW where to start with and replace the CORRECT parts... You should be able to save a few thousand bucks on new cats.....
Lexus Test Driver
Joined: Feb 2012
Posts: 1,158
Likes: 23
From: PA
My mechanic used double gaskets I think on the gaskets BEFORE the cats... Apparently the metal on the header manifolds were deteriorated enough that needed a lil TLC before finishing up the installation of the new cats. Not a bad idea to double up and gaskets.
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