Is there a more accurate test than a code reader?

My general plan of attack. 1, write down the codes. 2, make sure I wrote them all down correctly. For some reason my eyes see 1234, my hand writes 1243. 3, erase the codes, start & rev the engine. Check what codes came back. 4, above.

Quite often you can visually find an issue, cracked hose, hose came off, a wire worn through and shorting to ground.

Another good plan of attack is to do exactly what you’re doing. Ask others what they’ve found and how they fixed it.

 

I have an ‘08 Tacoma base truck with 418,000 miles. About a year ago the PO420 code came up on mine. I took it to a local repair shop in town and he immediately told me it needed a new catalytic converter which I think was around $1800.
My truck ran fine so I did some more research. I was told that a Tacoma with a lot of miles means the gas cap has been off and on a lot of times and that can sometimes cause the code to show up. I went to my local dealer and got a new fuel cap and put it on. The code has not come up since. Just saying.

 

Lots of good info guys, but do you all realize that the 1st post was over 1 year ago?
The person in post #16 brought this one back, and has P0420 and P0430, and nothing else.

It’s highly likely it’s the converter(s).

 

There are a few things that can set this code that need to be looked at first in order to rule out if the cat converter is bad or not. Leaks in the exhaust system and faulty o2 sensors not reading correctly.

How many miles are on your Tacoma? Have you taking it in on any rocky trails that where a part of the exhaust system may have rested/slid across on a rock? Does the code come back right away after clearing it, or does it take sometime for it to pop back up. The condition of that code is not detrimental to the motor unless there is a obvious lack of power. The lack of power would be from the cat converter being clogged/restricted and creating to much exhaust pressure. The code reader suggests that it's an emergency fix because it's Emissions related. And with both of us in California, you know how bonkers the California Air Resource Board and Vehicle Emission (smog testing) Tests are.