California truck in N.C. P0420 showing Weak Catalytic Converter Code

California CARB certified 2000 Tacoma needs to pass 48 State Federal Emissions.

Can I replace the two catalytic converter California exhaust with a one catalytic converter 48 state compliant exhaust or will the computer not recognize the new O2 inputs and still throw the P0420 code ?

Any ideas.....the Cali two cat system is really BIG BUCKS compared to the Federal emissions system.

 

The few states that still require emissions testing really need to abolish it!

 

The P0420 code could just be an O2 censor, or possibly an exhaust leak.

https://www.tacomaworld.com/threads/need-help-check-engine-light-code-p0420.195841/

 

https://www.urdusa.com/urd-rear-o2-simulator-2rz-fe-2-4l-3rz-fe-2-7l/

much cheaper and they work. I have one on my 2003, 2.4 in Mexico and it runs the mexican gas just fine, no codes. Best $120 spent.

just hide it under the seat with some clothes or ?

 

P0420 is rarely o2 sensors, the code if alone signifies that the sensors are working. Don't throw sensors at this.

We don't have diagrams on the cali exhaust on my system, but I imagine there is a visual check during the smog test. They know what to look for.

 

I did install two new Denso sensors....it was a waste of money.
Very tight exhaust.....no leaks.
128k mile truck I got it at 104k so I have no knowledge of how it was driven or cared for but it runs great and doesn’t use or burn a drop of oil.

I love the idea of the under seat sensor device : )

You guys are great .......thanks for all the replies.

 

I had the P0420 code, replaced both 02 sensors two years ago and all is well still on original cats at 470,000 miles. I shot a lazer temp guage on the cats and if I remember they were at 400 or 500 degrees, so they are working still

 

I got about 500’ at the first ( Cali trucks have two ) converter but the second cat ( I forget what it was ) not nearly as high a temperature.

Wasn’t sure if that was normal.....the first cat high temperature the second cat not so much.

I do show the code after about 20 miles of driving.

P.S......just trying to remember what the second cat temp was ( I’ll check tomorrow no time today) thinking it was maybe closer to 300’. Is it normal for the second cat to be that much cooler than the first one ? Thx.

 

I will check mine again but I don’t think 300 degress is correct, should be higher, I have one cat only

 

I had that code and and A/F sensor code a while back. Cleaned the MAF sensor and everything has went away. Worth a shot before spending bigger dollars.

 

I've had the code more than once. Changed A/F sensor, and also had leak before the O2 sensor. 168K on the OEM CARB cats, and still working. Maybe not your problem, but might help someone else.

 

I had a pinhole exhaust leak... barely noticable.. and it triggered this code. Welded hole closed 3 years ago and have had no problems since!

 

Mine temp is 490 some degrees so if your is 300 degress it’s probably no good

 

Thanks for checking it......so I guess both cats should be around 500’ (+ or - a little).....my second cat is probably 100’ or more likely closer to 200’ cooler than the first : (

 

Once I had the downstream O2 sensor gasket develop a very small leak....it threw the P0420 constantly until I fixed it.

 

This is rarely a bad catalytic converter, these things are meant to last the lifetime of the truck, and if they don’t you have a larger underlying issue. Mine was an exhaust leak which I fixed. Then I got p0420 as a pending code, after driving it it turned into p0186 iirc. Anyways it was the second o2 sensor which I replaced and fixed the issue totally. Look up how to vacuum test your exhaust, you can do it with a vacuum cleaner.

 

UPDATE.....took out new rear Denso O2 sensor ( left new Denso O2 sensor in front) and put back 128,000 mile used old sensor......

Hasn’t thrown the P0420 once now driving it many miles ( no exhaust leaks before or after switching O2 sensors)

The rear cat reads 100’ to 200’ less than the front cat so I know (???) the rear cat is weak, but somehow the old rear sensor doesn’t pick it up like the new sensor. I don’t know if this makes sense but maybe it will help someone else with a similar problem.

 

Your rear cat is naturally gonna be cooler than the upstream cat because the upstream one is going to dissapate the heat of the exhaust and the exhaust gases are cooler entering the rear cat.

Good to hear the O2 sensor worked, if it ain’t broke don’t fix it.

 

I have one cat at 500 degrees, I thought I had two as the truck was made in California

 

the old original sensor just might be slow in responding to O2 level changes and that is what the PCM is looking for a steady reading.