Yep, good old code 0420.....

So before anybody gives me the super helpful "use the search bar" suggestion, know this: I already did. I read 8 or 9 threads but nobody ever posts their answers so I never find out what it took to fix things. I know it's exhaust related, I just want to know where to start before I start buying a few hundred dollars of parts.

Could it be as simple as sealing some leaks in the exhaust? My exhaust system from the cat back is about 4-5 years old, the cat is original 2001 as far as I know. The upper O2 sensor is new, the lower is original (AFAIK). I have a hole in the rear right where it makes the final bend to the side.

If I do need to buy either a new cat or new O2 sensor, do any of you have preferred places to buy?

Thanks ahead of time.

 

Try cleaning the MAF.

Beyond that, the general consensus is that it's either the O2 sensor (or related wiring) or the cat.

This particular code seems to have some evil voodoo around it, from what I've read in most car-related forums. Some say it's related the PCV valve, vacuum leak, etc. For some of those things, I say, it doesn't hurt (PCV valve cheap and easy). How's your gas mileage? Has it dropped at all?

Don't forget that you actually have to clear the code to make the light go away. I don't mean to insult your intelligence, but if I had a nickel for every time I've read "I did X, Y, and Z, and the light stayed on", I'd be able to buy myself a new cat. If you don't have a tool for that, you can clear it by disconnecting the battery. Would you believe I've actually seen someone post somewhere (a general toyota forum, I think) that the auto tech fixed it by disconnecting the battery? Egad. That guy got robbed.

Which reminds me, did you clear the code first and see if it comes back? Sometimes it's a voltage/wiring thing (which you could test to eliminate the O2 sensor(s) from your list of suspects). So my suggested plan of action to start would be to clear the code if you haven't, then clean the MAF sensor, and maybe replace/clean the PCV. Those are easy and don't cost much.

 

It just came on this morning as I was driving to work so I haven't been able to do anything yet, but I'll clear the code when I get home and check my exhaust for leaks first and see what happens. The anti-foul plug idea is a new one, I may try that before replacing O2 sensors or the cat.

 

I was fighting this code for a while. I have a 97 2.7 4x4 5 speed with 157k. The previous owner put a header on it and tapped through the cat when it clogged or rattled. My solution was to weld a few leaks in the exhaust, replace both o2 sensors, and use a urd exhaust simulator on the downstream o2 sensor to make up for the cat not being there.

I was code free for a few months now I'm messing with po401.

Use rock auto if you buy o2 sensors. They ship fast and two oem denso (do not buy non oem on this) ones cost as much as one from a parts house. Good luck.

 

@ruler1:

My 97 Tacoma 2.7L 4x4 (auto tranny) is in need of O2 sensors. Rock Auto lists the front and rear as the same part number, but the dealer says they are different parts. Tacoma service manual just lists different resistance values they are supposed to be at but says nothing about the part itself. Local parts shops also disagree if they are the same or different parts.

Any help you can offer is appreciated.
Thanks

 

I think I found the cause of my 0420 code, I have a massive exhaust leak in my muffler, plus my exhaust hangers had rotted through and the exhaust was shaking like a lunatic. I put new hangers on and I'm going to go to advance auto tomorrow and get some muffler puddy and tape and patch the hole for now. I don't have enough money to get a new muffler, plus the rest of the exhaust behind the cat is rusted and worn out so I'm going to save up and buy a cat-back exhaust system, I'm thinking Gibson full cat-back exhaust and muffler. and

EDIT: I'm looking at the Gibson site and they only list an exhaust system for the 2wd 2.7L, not the 4wd. Is that the same part? Any other suggestions for an exhaust system for a 2.7L 4wd xtra cab?

 

My 97 2.7L 4x4 is a reg cab but I got a cat back welded exhaust system (Bosal) from Auto Parts Warehouse for $132, free shipping late last fall. Used a sawzall to cut the 2 bolts and bolted the new one in place. Fit perfectly at the hangers and the O2 sensors. Mine came FedEx.

Current Coupon APW3182012UP is for 15% off $150 or more. Expires on the 18th (tomorrow).

http://www.autopartswarehouse.com/

 

On the o2 sensors: They are the same. I was confused when I bought them too. I emailed rock auto, they double checked, and I installed.

Use plenty of PBS blaster. I broke studs and had fun getting the nubs out. Again, they are the same upstream and down.


On the exhaust: just go to a muffler shop. Our trucks are easy and a custom system made by a muffler shop is gonna be cheaper than a kit. I had a dynomax mustang muffler put on mine and it sounds good. Any stock newer mustang gt (the gt's were stainless oem) takeoff muffler will sound great and not sound like a fart cannon.

 

It looks like Gibson exhausts are going to be around $350, are you saying a muffler shop could do it for less than that? I'll have to call around and get some price quotes, I just assumed doing it that way would cost more just because of labor costs. Back when I lived in an apartment and couldn't do my own work I had to pay about $900 for a full exhaust system to be installed.

 

I spent 70 bucks having my muffler installed and fixing several exhaust leaks. I could of had custom dual exhaust with chrome tips for about 250. Find an exhaust shop. It should not cost more than 500 unless it is part of a turbo setup.

 

To close out my thread and make sure it isn't another one of those "what was the final result" type things - my issue apparently was an exhaust leak. I got under and looked things over and like I said, the muffler had a massive leak in it. I patched it using exhaust tape and while it isn't 100% fixed it is much, much better and my CEL hasn't come back on since the patch. It's only a matter of time until the rest of the exhaust rots away so now it's on to finding the best deal for a new cat-back setup.