P0420 code on '01 tacoma v6

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Mar 30, 2007
A few days ago my CEL came on. Took it to Autozone and got the code, but not specific on the solution or problem.
153K well maintained miles.
AND today I was slowing down to turn off the highway and my truck stalled, I pulled over and after a few attempts and with the accellerator depressed it started. It started the rest of the day fine too (6x).

What may be the usual order of fixing this?
Should I clean the MAF or anything else?
New fuel - and see if the CEL comes back on?
New O2 sensor at a tune of $130/ea?
New cats at $700?

Any suggestions?

As usual, the cheaper the fix the better! :cheers:
Here is the OBDII code list and probable causes for the 5VZFE engine it is from the 4Runner faq but it will be the same for the taco.

Looks like it might be time to get new A/F sensor and oxygen sensor by the FSM.

I think I remember reading they have about 100,000-120,000 mile lifespan typically.

I know there are countless P0420 code threads on TTORA for reference also.

I have no first hand experience with that particular code myself.



If you read my post here: https://forum.ih8mud.com/95-gen-toyota-trucks/384253-3rd-gen-4runner-o2-sensors.html I just went through replacing both my A/F Ratio Sensor and am waiting to recieve my rear O2 sensor. My advice is to use Amazon.com and buy the Denso sensors as that was what came in the Toyota box for the A/F Ratio sensor. Amazon is WAY cheaper and has both direct fit and universal (depending on how much you want to save...).

Good luck,

That was the first code my 03 Tacoma V6 showed. It came on at 60K which I thought was too soon, but I found others on TTORA that had the same problems.

I bought the O2 sensor and the problem was solved. Here's a writeup on replacing it:

4Runners.org - Changing Your 02 Sensors

I recommend ordering it through a vendor on here or another forum that will make sure that you get the right sensor. Apparently, they are different between years, manual, auto, etc...and one size does not fit all.
I had Autozone turn off the CEL and it hasn't come back on after several tanks of fuel.
I will clean the MAF this weekend as it's never been done....
I am keeping my fingers crossed that the CEL stays off since CATS are expensive!
When it comes on again, I'll change out the O2 sensors.
Thanks for all the suggestions and links!

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