Check engine Light with code p0430 fixed for less than $30

I thought it was pretty easy overall even though it seemed to in sort of a hard to access location. It is located on the top left side of the engine behind the radiator cap. Maybe with the right tools it would have been a lot easier but this is what I did to replace it.

Based on my best recollection:
First I removed the wiper arms, simply slide off the black plastic cap to expose the nut that holds them on. Take note of the exact angle/position so you can put them back on without having to readjust them like I did. When the arms are off you will remove the plastic cover that spans the width of the car at the bottom of the windshield. There are black clips that need to pushed back to let that cover pop off. Then unplug the connections to the wiper motor and remove that. Then there were about 8 silver screws holding the metal cowling down... all that was easy! The hardest part for me was moving the retention ring up the rubber hose as I did not have a good long pair of pliers to make that easy, my pliers just did not reach it very well. It took a little while to remove the pcv valve itself as I was unscrewing it from the valve cover, I was only able to get about a 1/4 turn on it with the wrench I had, not a big deal, just a few extra minutes.
If anyone else reading this post knows of a better way, hopefully they can let you know.

I say try it and see if it works, it could save you a lot of money if that is what is triggering the code. I would also double check the code itself, mine was a p0430.

If the air filter and PVC valve replacement doesn't get rid of your P0420 or P0430 codes ... here's another inexpensive fix.

The following would only work in areas that do NOT use a tail pipe sniffer for emissions testing ... they simply check for check-engine lights. Tailpipe emissions are unchanged, but we don't have emissions testing around here at all. Obviously, this fix is not recommended if the CATS are physically damaged or corroded either.

I just had this problem on my 2004 Sienna, with over 300,000 miles, but I had both P0420 and P0430 ... so both my CATS were bad. I couldn't afford to have both replaced ... so I used the Radio Shack diode fix.

Rather than replace the CATS, I soldered a standard Diode from radio shack (P/N: 276-1141) into the sensor lead (blue wire on a Denso O2 Sensor) of each DOWNSTREAM Oxygen sensor (silver diode marking must be TOWARDS the 02 connector/ECU).

I've done this on a couple of Pontiac Vibes too (really a Toyota Matrix) with the P0420 ... and it works! ... the light goes out. The diode reduces the voltage sent to the ECU, which "fools" the ECU into thinking the CAT is working fine. The downstream O2 sensors don't control or affect engine management ... they simply monitor the CAT efficiency.

I've put about 1000 miles on my Sienna, and about 7000 miles on my Pontiac Vibe GT since the fix ... and the Cat codes have not returned.

Hey guys,
The internet can be a wonderful thing. My 2005 Sienna with 150,000 miles had the Check Engine Light (CEL) pop up after making a 600 mile trip to visit family over the holidays. Code that came up was P0430 "CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 2)". After following some of the suggestions on this forum, the CEL turned off and I was able to get the State Inspection passed. A big THANK YOU to those on this thread that took the time to post.

Quick summary:
I changed the air filter ($14), filled the tank with Premium gas plus a Techron additive ($4.50 + $0.50/gal more for premium -$7.00) and changed the fuel gas cap ($30). Drove it for 338 miles and the CEL did not come back after making a stop for gas. Inspection done 1 day later and passed.

Long story:
As I mentioned below, I was visiting family when the CEL came on. It is also the month that my car registration and inspection is due. I was bummed after the Auto Zone clerk gave me the code reading. He offered a Universal Catalytic Converter for $140. I passed and decided to call a friend of the family who is a mechanic. He said he could take care of it, but recommended that I replace the CC with an original Toyota part, as he has had problems in the past where the CEL comes back after replacing a CC with a universal one after only a few days.

So, I called Auto Zone back, they said they could get it for $350 or so, but would need to be ordered. Didn't work for me if I wanted my friend to replace it since I was driving back home in 3 days. That evening I thought I would check the internet to see where I could get the part and I stumbled into this forum late in the evening. (Thank you, again!) I read about changing the air filter, gas plus additive idea and PCV valve.

The following morning I called the dealer, and he quoted the OEM Cat for $600. But, to my surprise, he said that he would recommend stopping by and starting off by buying the fuel cap. He said not to buy one from the auto parts store, to buy the original part from them. He recommended to try that out and clear the CEL and see if the light came back on. He also said that it may work, not a guarantee, but it would be better to spend the $30 instead of the $600+. I figured I had nothing to lose.

I changed the air filter (standard from an O'Reillys), which was plenty dirty and one of the screws that holds the lid was missing, filled the tank with fuel plus additive (set trip counter to 0), and drove to the dealer for the gas cap. After a couple of days driving in town, the CEL was still on. I had traveled maybe 120 miles or so. Came time to head back home for the 600 mile trip and on my first stop, 200 miles in or so, the CEL did not come back on! Trip counter indicated 338 miles traveled.

I made it safe home and the next day went to get the Sienna inspected and renewed my registration. All good!
Thanks again for posting your experiences. I would not have tried other alternatives, I was ready to get the catalytic converter replaced and would have spent hundreds. Hopefully somebody will read mine and save themselves some cash too. The internet can be a wonderful thing.