Patrickleo

I had the catalytic converter replaced recently, and also I replaced one o2 sensor that had gone bad. (bank 1 sensor 1).

Now it seems I need bank 1 sensor 2 replaced, (p0141) are the other codes just the same problem? or is there something bigger wrong that I'm not aware of?

Which denso o2 sensor do i need?

Docstrange

I had a similar issue with my 2003 GS 300 Lexus and the mechanics just took my money. The real
pro I think you may have is an air box leak that will cause those issues. My VSC and Check engine lights along with different codes such P0430, P0420, and a couple of others I can't remember off the top of my head. The mechanics said I needed all 02 sensors changed, (went down the road you are traveling only to find out that the main cause was the Air Box in between the air intake that holds your filter and the manifold intake. I have the inline 6 cyl 3.0. The underside of the air box became brittle and was cracking and falling apart creating a bigger whole. It caused the car to hesitate so bad that the car would lunge. Forward which creates another issue. It ran rough. I brought that to the mechanics attention and showed him a picture of the cracking and gaping hole. He was nice to buy a new air box for free. Well since I spent close to $2000 grand trying to fix it. I was pretty sure he would do that sense I never needed the new sensors. So check this out yourself first. Your car should be somewhat similar to mine I believe. I hope it helps.

tomf

I'd replace the sensor first to see if that fixes the problem. It's cheap if you do the replacement yourself.

Denso part number 234-4064 from Denso part finder http://densoautoparts.com/find-my-pa...icle-selection at Amazon https://www.amazon.com/Denso-234-406...words=234-4064

yeskay

seems like a vacuum leak. i would suggest repalacing the air box hose as Docstrange mentioned.

Patrickleo

Along with check engine light, these lights are on.
I replaced the one Sensor for bank 1 sensor 2, and most of the check engine codes cleared, except for P0430 still remains, it says "Catalyst System Efficiency Below threshold, (Bank 2)".

Thoughts?

iwayman

My 2002 ES300 has been showing P0430 and P0420 codes couple times. The 1st time was about 1.5 years ago I switched to 100% to 93 Octane gas and it fixed it (I used to mix 60% 93 Octane with 40% 87 Octane to save money). This 2nd time happens just about 2 months ago and I notice my mpg went down from 28mpg hwy to only 24mpg hwy. I'm was searching for the cure and found Scott Miller's youtube video recommending putting 1 gallon of Lacquer Thinner into a half-full gas tank and drive for 150 miles at high speed. I just did it using Home Depot's $16.47 a gallon Lacquer Thinner and about 9 gallons of gas in the tank. I drove non-stop for 120 miles at speed 60 - 78 miles/hour. After 120 miles, I stopped to for a bath room rest. Lo and behold, when I restart my car, the check engine light went out all by itself. I think the catalyst did got clean up with Lacquer thinner.. I also notice my mpg is going back to almost 28 mpg. So it cost me just $30 to fix the P0430/Check engine light. The cost of the Lacquer thinner and 5 gallons of gas to drive 120 miles. I hope this help many of you in the future. Happy New Year!

verbatim

were you able to fix this p0430 issue?

Docstrange

On my Lexus GS300 I incurred multiple codes over the years from 2012 - 2019. In 2012 I ended up changing all four O2 sensors that was diagnosed by a Repair shop. Turned out it was a small air leak that caused these issues. Air leak was right at the air box going into the Air intake system Manifold. Check that first to ensure no air leaks exist AT ALL. This kept my car running until 2018 and started getting the P0430 & P0420 codes. No matter what I did, it would come back on in the next few days or even up to two months. I changed out all of the O2 sensors again thinking this may be the issue. I also had oil leaking from my seals in he front of the engine. I thought by fixing that it could play on with the condition of how my fuel was burning. I ended up taking my car to a reputable repair shop who diagnosed the catalytic converters as being the problem. I also came up with the same results by using the diagnostic tool reading each O2 sensor. I paid $110.00 for the shop to tell me what I knew. They could have changed the exhaust with "cats" for 1500.00 total. I ended up buying an after market one for 1100.00 and changed it myself. It took me about 4 hours due to me being older and having to tough it out lying on the ground. it was not hard to do after removing the nearby accessories. So, there is another thread on here that details how to diagnose you situation, so I will not try and duplicate that. He did an awesome job detailing that process. My GS 300 HAS APPROXIMATELY 300K miles on it. it is now running like it should run with no issues for the last three months. If it didn't fix it, I would be selling it for parts, but with the timing belt change, fixing the oil seals in the top end of the car and the exhaust system fix, I should be able to drive it another 100000 plus miles. It still gets 24 miles on the highway which is impressive to me. Hope this helps. You may need to CHANGE your "CATS".....