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My LS460 with 135,000 miles gets these two codes occasionally and I clear them out then sometimes days or many weeks later they pop back up. I’m looking to sell the car soon I’m the 2nd owner I’ve had it over 15 years with no problems. Thanks for any help or suggestions.
I am currently going thru this with my 2014 with 320,000 miles after I ran a can of seafoam thru the intake. P0430 is Bank 2 (passenger) and P0420 is Bank 1 (driver) issue with the cat converter, there's a mismatch between what the O2 sensors are showing and what the computer expects. For me I am able to graph the voltages between the upstream and bank 1+2 (4 total) both downstream banks should show the same constant voltage (.9 to .7 ish) thru the RPM range 1,000 thru 3,000. (you can look at the upstream ones too to see, they are around 3.3V) If you see random dips / drop outs of the signal then it points to an o2 sensor failure. For me my Bank 2 sensor 2 (downsteam) stays at .8V at 1000, but through 2100 till 2900 it drops to .5 to .6V, above 3,000 rpm it goes back to the expected .8 to .7V. So I think the seafoam just fouled the sensor enough to throw a code (they are OEM ones with 300,000 miles on the clock). ?
The reason you are able to clear it and drive without a code for 1 cycle is there is a short ECU relearn, and a long ECU relearn loop (or at least that's what a good car friend of mine said). Where the computer needs at least 1 short cycle, and 1 long cycle to determine what the "nominal" sensor states should be. if it falls outside of that then it'll throw a code.
Hopefully both your CATS aren't bad. That would be costly. There's a Scotty Kimler video out there where he says you can clean your cats by running Paint Thinner directly in the intake. Idk?
I am currently going thru this with my 2014 with 320,000 miles after I ran a can of seafoam thru the intake. P0430 is Bank 2 (passenger) and P0420 is Bank 1 (driver) issue with the cat converter, there's a mismatch between what the O2 sensors are showing and what the computer expects. For me I am able to graph the voltages between the upstream and bank 1+2 (4 total) both downstream banks should show the same constant voltage (.9 to .7 ish) thru the RPM range 1,000 thru 3,000. (you can look at the upstream ones too to see, they are around 3.3V) If you see random dips / drop outs of the signal then it points to an o2 sensor failure. For me my Bank 2 sensor 2 (downsteam) stays at .8V at 1000, but through 2100 till 2900 it drops to .5 to .6V, above 3,000 rpm it goes back to the expected .8 to .7V. So I think the seafoam just fouled the sensor enough to throw a code (they are OEM ones with 300,000 miles on the clock). ?
The reason you are able to clear it and drive without a code for 1 cycle is there is a short ECU relearn, and a long ECU relearn loop (or at least that's what a good car friend of mine said). Where the computer needs at least 1 short cycle, and 1 long cycle to determine what the "nominal" sensor states should be. if it falls outside of that then it'll throw a code.
Hopefully both your CATS aren't bad. That would be costly. There's a Scotty Kimler video out there where he says you can clean your cats by running Paint Thinner directly in the intake. Idk?
Thanks so much I’m not an auto tech guy I know enough to be dangerous lol I need to find a good honest mechanic that knows Lexus in South Jersey I’m hoping it’s not the Cats. Thanks for your input
Hey anytime! Funny when I had the same issue and you posted this. I was just up in Millville NJ at the NJ Motorsports Complex for a 24 Hrs of Lemons race this past weekend. So much fun! I do highly recommend. Hope you get it figured out!
So I've been reading into this more (with my new O2 sensors I still have the P0430 code). Soy you can use a spark plug de-fouler to space the O2 sensors off of the exhaust pipe. It'll trick the system to thinking its still OK. (Dorman HELP! Spark Plug Non-Fouler - 42008). Then I've searched the forum and if you have an exhaust leak that'll cause an error too. Lots of LS430 owners say the heat sheilds at the Y-pipe cause rust spots under them For that you need to get a new section of exhaust pipe welded in.
I am currently going thru this with my 2014 with 320,000 miles after I ran a can of seafoam thru the intake. P0430 is Bank 2 (passenger) and P0420 is Bank 1 (driver) issue with the cat converter, there's a mismatch between what the O2 sensors are showing and what the computer expects. For me I am able to graph the voltages between the upstream and bank 1+2 (4 total) both downstream banks should show the same constant voltage (.9 to .7 ish) thru the RPM range 1,000 thru 3,000. (you can look at the upstream ones too to see, they are around 3.3V) If you see random dips / drop outs of the signal then it points to an o2 sensor failure. For me my Bank 2 sensor 2 (downsteam) stays at .8V at 1000, but through 2100 till 2900 it drops to .5 to .6V, above 3,000 rpm it goes back to the expected .8 to .7V. So I think the seafoam just fouled the sensor enough to throw a code (they are OEM ones with 300,000 miles on the clock). ?
The reason you are able to clear it and drive without a code for 1 cycle is there is a short ECU relearn, and a long ECU relearn loop (or at least that's what a good car friend of mine said). Where the computer needs at least 1 short cycle, and 1 long cycle to determine what the "nominal" sensor states should be. if it falls outside of that then it'll throw a code.
Hopefully both your CATS aren't bad. That would be costly. There's a Scotty Kimler video out there where he says you can clean your cats by running Paint Thinner directly in the intake. Idk?
Thanks so much for your expertise and advice I’m going to bring it into a good repair shop at the end of the month so we shall see what happens. I don’t want to sell it with this problem.
06-12-24, 03:26 PM
HELP PO 420 PO 430 keep popping up 2007 LS460L
