Can my "cats" really be bad?

I have a 2004 Tacoma with 74,000, very easy miles on it. Is it possible that the "cats" are really bad? I'm getting a CEL and the P0420 code. It's intermittent, I get the CEL and then check the code and clear it and then can drive for a week or two and then it comes back. I've read many posts here and on other forums, and spoken to a retired Toyota mechanic about it. I think I'll start by replacing the O2 sensors and then if that doesn't fix the problem will replace the cats, but is it possible that the cats could be bad with only 74,000? Has anyone else had the PO420 code with low mileage, and if so how did you fix it?
Also if I follow the service manual and check the O2 sensor plugs with a volt meter, how accurate would that be because of the intermittent nature of the problem?
Thanks for any help you can give.

 

I just replaced the cats in my '04 xtracab back in January, and only have 78,000 on the odometer. I bought it with 66k miles last fall, and within the first 500 miles I drove, I got the P0420 code. Turned out my front O2 sensor was bad, so I had that replaced, but the code came back within 100 miles of clearing it. I took it into my mechanic and got the bad news; cats were bad. So I bit the bullet finally and had the cats replaced. I freaked because after that the code came back, but I cleared it and have been fine for awhile. Hope you don't have to replace the cats, but if you want to kill that code, you might have to.

 

Thanks for the replies.
Crock - Do you know how your mechanic determined the O2 sensor was bad, and did you go with OEM cats? Thanks again for the help.

 

You can usually find out easily thru continuity or other means to find out the O2 sensor's bad. Oem cats are the only way to go on these trucks last time I checked.

 

Cats can definitely prematurely deteriorate.

I used to be a Toyota tech here's a trick you can do to "revive" your cat:

1. Remove the Cat.
2. Spray the "honeycomb" with carb cleaner (empty the whole can into it) make sure you collect the residual spray dripping out into a container and dispose of it.
3. Hold the Cat over a 5 gallon bucket or container and take a garden hose and wash spray the "honeycomb" for a few minutes.
4. Re-install the Cat.
5. Clear the code, run monitors, and pray it passes the Cat monitor.

I've done this to my own truck and got the Cat to last up until 194k. Usually when you get a p0420 it is definitely the Cat. At the Toyota Dealership we used to use a laptop scan to inspect the Cat with A/F & O2 sensor flow charts. If you take it there tell them you want a p0420 diag but it'll probably run you $100.

If you need to replace the Cat I'd highly recommend the Magna Flow. It's the bang for your buck. I got mine installed with flange mod (TRD Headers) for $277. OEM will run you $600+ (keep in mind I saw many OEM Cats last 200k+). Go with the Magna if you're on a budget. Go with the OEM if you're ballin'.

Good luck!

 

Last summer I had the 0420 code. Using the FSM procedure, I tested the front A/F sensor and the rear O2 sensor, only to find the rear O2 was bad. Costed me $40 to fix. Do simple tests before spending hundreds or thousands on a new front or rear cat. Check the full exhaust for leaks. Check the intake and outtake temperature of the cats while running. Use a multi-meter to test the two sensors' voltage and resistance according to the FSM. Check each sensor's seal. Sometimes the gasket rots away and causes a leak. Hit your cat converter lightly with a rubber mallet to hear any lose material. If this all fails, then look into replacing the cat converter.

 

First of all, thanks everyone for your responses. I thought I should give you an update on the PO420 CEL. I have been CEL free now about two months. My best guess is that the summer grade fuel is responsible for this stroke of luck. This is something that my former Toyota mechanic said might happen. If this is the case, I guess I can expect the CEL again sometime in the fall. I was told the CEL comes on if the system falls below 95% efficient, so I must be at right around that mark. I still have the same plan, when the time comes, I'll start with the sensors and then replace the cats. I'm hoping to find a exhaust shop to do the labor if I supply the OEM parts. I think I know a shop that will do this for me and I don't want to tackle the job, I live in Minnesota and the rusty exhaust parts are not my idea of fun.
Thanks again.