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Adding my experience to this P0430 topic with my '06 Sienna Limited with 166K. I was driving from Florida to New York and that DTC and the VSC light popped up while on the highway. This had to happen a week before my NYS inspection was up. I went through the troubleshooting sequence of air filter change with Seafoam, then PCV replacement, and then gas cap replacement. Still the code lingered. Pulling my hair out and dreading a possible cat replacement, the code was finally gone after replacing the upstream bank2 air-fuel sensor. Thankfully bank2 is in the front and easy to get to.
Thank you to all who posted the troubleshooting and background info on this code. Such an annoying code to deal with. :)
 

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My van 2006 with 160k also has p0430 came up, did all the free stuff first, but code still pending, and I used the Toyota techstream software to monitor the all 4a/f and oxygen sensor, and found bank 2 oxygen sensor is lazy, $50 densor from rockauto fixed my check engine light, I think the key is not to ignore the light, address the issue asap to avoid damage to cats
 

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I've got this too. Replaced the front bank 2 o2 sensor and still seeing it. Air filter is replaced every 3k miles or so. Guess I'll try the PCV Valve next.
 

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Gonna try this today..the check engine light has been on for me and now smog is due..but the code was a mass air flow code (can’t remember the code of the top)..so I got some cleaner, sprayed it and rest the monitors..just finished a drive cycle and the light came back on but now it’s showing this cat code...I did notice some surges when starting at a green light...I’m gonna go get the filter and valve and see if that works but maybe somebody here who knows better can pinpoint the problem better based on the codes I’ve had so far?
 

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Mine has 110k miles, 2004. i changed the pcv valve and air filter. then i changed the air/fuel on the front of the motor with a generic one.. my issue has always been intermittent. The front air/fuel started getting a circuit error, and continuous intermittent bank1/bank2 errors. I decided to go with denso air/fuel and oxygen sensor before dropping 570 on a new cat. it's been a couple of weeks and no more error. no way my cats should go bad at 110k miles. i'll repost here again if i do need to change my cat. That will be next if the error comes back. i've never had a car that had a bad catalytic ever. most i drive them is to around 150k, gonna have to keep this longer since i love this van.

make sure you all have and OBD2 reset tool.. you need to reset your computer after every change you make to the emissions system. you must drive around for 20-30 miles and see if it comes back. if it's immediate, you have a problem.
 

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I have the same problem (P0420); has anybody had experience of eliminating this code with air filter and PCV valve?
on some vehicles the generic DTC P0420 companioned along with DTC P0430 would be banks 1&2. As in cylinders 1,3,5,7 being bank 1 and cylinders 2,4,6,8 being bank 2. Hope you had luck with your project
 

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Mine was as simple as replacing the air filter. It's the cheapest and easiest 'fix', so it's a good place to start.
 
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