For the last few months I've been going round for round with this dang 420 code. I've since replaced both O2 sensors, MAF, spark plugs and wires. The best luck I've had of it not popping back up was running pure gas. I have an ultra-gauge so I'm able to check and clear the CEL when it comes on. I'm just tired of driving and waiting for it to pop up again. I've researched it to death and seems all I have left to replace is the cats (which isn't happening) way to much money. I've been toying with the idea of high flows and an O2 simulator. But I want that to stay as a last resort. I know there is loads of threads on here about this code mostly because I've already read most of them which has got me to where I am now. I don't know what else to try. Any help would be greatly appreciated

2002 T4R Sport Edition 4WD 167k miles

This was an interesting idea.

http://www.toyota-4runner.org/3rd-ge...ator-%245.html

Whats the big deal just replace the cat.

Those cost way to much. And the after markets are crap

With the amount of money you're going to throw at a multitude of variables to make the code disappear, you might as well just replace the cat with an aftermarket. I replaced mine with an aftermarket in November 2012 from a trusted local muffler shop and have put almost 40K on it, never had an issue. Unfortunately I can't remember what brand it is. To make a blanket statement that all aftermarkets are crap is a falsehood.

I've just read so many posts about the aftermarket cats none of which had good things to say so I was wanting to stay away from it. Finding that trusted muffler shop will be a shot in the dark also. It's not a complete no though. I've thought on it a lot and a buddy of mine has an 02 tacoma with no cats and no CEL so I know it's possible. In the end it's looking like a high flow cat magnaflow muffler and an O2 sim if I need it. Unless someone can suggest an easier route. Or has had luck with a certain aftermarket brand

Also it has 2 cats. Doesn't that mean it's one of the California emissions vehicles. Or did all of the 2002 models have 2 cats?

Agreed, Cats are cheap now. When my original cat went bad back in 2004 (only 5years old) Toyota wanted $1500. LOL yea right! I found a rebuilder online for $350 & sent back the core. It's still in there to this day & has out lasted the OEM by (10-11 years).

You could try seafoam to see if it helps. It did on my M20

Cats are not that expensive and if you can wield or know someone that can its pretty cheap. Get Magnaflow ctpats they flow well and last unlike cheap cats. Look on ebay or amozon. You might also find someone parting out a 4runner that will sell you the cats.

Tried seafoam and cataclean. No luck.

Do you remember where you got the rebuilt one from? That sounds like the direction I'm wanting to go.

LOL, that was 10 years ago. Google is your friend.

Just finished up with your suggestion. No more pending codes are showing on my gauge. I guess only time will tell but thanks for the help!

Good luck, worth a shot