P0420 Catalyst System Efficiency Below Threshold (Bank 1)

Greetings,

i have Tacoma 2001 2.7L 2 doors base, I changed the muffler but because the muffler was very rusty, the mechanic had a hard time to remove it so he had to hit with the hammer and kept shaking it so it finally came out and he was able to put a new one but then after driving it I got the check engine light! So I went and changed the downstream O2 sensor but still the check engine light still there, so what do you guys suggest? Should I change the Catalytic converter Bank1? If so, which one is Bank1 front and or rear? Do you have any suggestion from where I get the part for a good price online?

Thank you so much for your help

 

Hello Adam
Welcome to TacomaWorld
The 4 cyl 2.7L only has 1 bank.
Sensors are B1S1 upstream before catalytic converter. S1 on 2001 2.7 is an air/fuel sensor not associated with catalytic converter.
B1S2 is downstream O2 sensor which measures catalytic converter efficiency by measuring remaining oxygen in exhaust gas after combustion in catalytic converter.
Exhaust leaks upstream can throw P0420.
Check for leaks at manifold and Ypipe donut gasket where Ypipe bolts to catalytic converter.

 

this code is not self clearing... see if auto zone can clear the codes for you. If it comes back on in a bit get back on the forum.

 

I dealt with this for a while and finally got tired of clearing the CEL. The only thing that actually worked was replacing the catalytic converter. I was able to get a good deal on CARB compliant bolt on front and rear from rock auto, and scrapped the old cat for almost what I paid to have installed ($120).

Edit: I checked and prices have really shot up in two years. I was able to replace both sensors and front/rear cats for $600.

 

I did clear it and it came back after I drove it for 40 miles!

 

^^ same for me. I think this is usually the case for most people whether they want to admit it or not.

I also got 2 CARB Magnaflow cats installed for $600 almost 5 years ago. But cat converters have shot way up in price because the platinum/palladium/rhodium metals used in them have skyrocketed in value in the last couple years. China started implementing stricter emissions laws on it's vehicles which drove the price of the metals way up.


Although the fact that this code popped up for the OP right after getting his muffler replaced is odd, might just be a coincidence though.

 

I would check that the beating on the muffler did not cause any of the gaskets to fail between the cats which will cause the code.

Even a crack in the pipe would also trip the code.

 

Which pipe?

 

Anywhere on the exhaust, before the rear o2 sensor. Any cracks after the rear o2 won't matter.

Cracks before the rear o2 sensor mess with the readings it gets and can trip a code

 

Ok I will check, do you have any good website where I can buy the cat from? Thanks

 

Rockauto is a good place, or any local exhaust shop should have the ability to get you something good like Magnaflow or Walker brand.

Does your county/state require strict emissions testing? If so you'll need one of the CARB/50 state legal cats, there are several aftermarket options for our trucks though luckily. Newer vehicles usually have to get OEM ones and they are $$$$$

 

If it is an exhaust leak turn on engine and spray from manifold to cat and further down with soapy water

 

I also have had the p0420 code for awhile but I keep clearing it. Anyone know if you can run a federal cat on a cali emissions truck? One just one cat? Don’t live in an area with emissions testing. Sorry to threadjack.

 

If your county doesn't require emissions then it should be fine. I have wondered though if the cheaper cats with less material in them will result in a P0420 code sooner, but I'm not sure.

 

Yeah, it’d be a lot cheaper to replace with one federal cat or something and see if the code still pops up then I could one of the URD O2 simulators I guess.

 

Old thread, but I have a 01 2.4 that has two cats. How do I check if this is cali emission vehicle or not? Been Fighting this 420 code and so did the previous owner before selling.

 

Idk how you figure out the California emissions thing but I'm pretty sure your 2001 needs to pass. Have you checked for exhaust leaks? That's the most common cause of a P0420 code.

 

I have. there is a terrible aftermarket cheap muffler that some clown shop welded on there. Would it be worth getting a better muffler ?

 

The muffler doesn't matter. Have you done a temperature test to see if there is anything wrong with your cats? How did you test for a vacuum leak? How do the welds look where this muffler was welded on?

 

muffler welds are terrible, worse I have ever seen. No temp test, I have a temp gun what's the best way to test? I replaced all vacuum lines, o2 sensors, maf sensor, spark plugs, gas cap. Used all Denso or OEM parts. Truck feels low on power. I had several CEL when I bought the truck. all have been fixed except for 420 code. it comes and goes.