First, I live where there are no inspections.....that might effect some answers....
so my new to me has two issues related to exhaust.1) 420 code which is usually rear sensor from my experience. 2) System is completely rotted out.
P.O ran it on 4 cylinders for who knows how long due to bad coil and single electrode plugs, so all that raw fuel was dumping into cats. Dont know if damaged the cats. ( bought it as a fixer upper, running bad and check engine light for P420 code.) with tuen up of plugs, wires and new coil it runs great. Check engine light clears, and back within a few miles with same code.

1) live where there are no inspections
2)) of course exhaust shops want to do both cats due to pipe conditions. $$$$$$ they say they have to replace both cats casue it left the factory that way. Priced cat back systems, but...what if I need cats ?
3) have the oppurtunity to get a earlier system with one cat , off a 2000, ( one cat was normal for that non california style year) that appears to have no rot, would have to get a new pipe for the front made up with a bung for front sensor, or spend the $$$ on a new front cat

questions ??????

1) will the front pipe from the 2000 fit and replalce the 2001 front pipe that has the first cat.

2)do I need the front cat ? Will the computers be an issue on the 2001 for not having that front cat, but it WILL have both sensors...both denso


thanks

I've put a little bit of research into this as Toyota made Federal exhaust 4Runners through the model year 2000 (which mine is one of them even though it was sold in CA) and also CA emission vehicles with two cats from 99-02.

The difference between them from a sensor standpoint is that Federal emission vehicles come with a narrowband O2 sensor and the CA or two cat emissions vehicles have a Toyota wideband (operates on a 0-1V signal instead of standard 0-5V). The part that is unknown is, can you put your wideband or Air/Fuel ratio sensor and put it in a narrowband exhaust port? Does it fit, does it read correctly, etc.? That is what you would have to experiment and find out. Everything else doesn't' really matter that much, pipe can be bent or cut or welded in.

Magnaflow makes decent catalytic convertors with warranties. I got a CA ceramic one for just under $200. Federal are even cheaper.

To answer the question is the front cat needed, I would say no. The single cat vehicles pass smog with flying colors. Mine was near perfect with almost 0 emissions.

The flange connection is different between the 2 styles where the manifolds/crossover pipes connect to the exhaust. The California system has what appears to be a more standard 3 bolt flange, the FED emissions trucks have a weird 2 into 1 oblong shape flange, so a Fed emissions take off pipe with cat as is will not directly bolt up to a Cali emissions flange.

Not sure if the only having 1 cat would throw off the upstream A/F sensor/ECU on the 2 cat Cali emissions system.

The A/F sensor is before the first cat, so essentially it doesn't even know if the exhaust has one or two cats. It would have no impact unless it doesn't fit in the narrowband flange.

Gotcha, didn't they change the sensor mounting style from bolt on flange to screw in or vice versa at some point? On both the 2000 FED (Canadian) and Cali (US) trucks I had the 02 and A/F sensors were all bolt on flange type.

Yes, it would. That's because the computer is factory set to stricter emissions standards on the two-cat Cali. versions as read by after cat O2 sensor. The reason for the two cats is to meet those stricter standards. If you run a Cali ECU with one cat, in theory you should end up setting a P0420 because cat efficiency is lower than spec. It's hard enough keeping the Cali. computers happy with both cats. As far as engine performance and economy, you are correct.

2001 and 2002 got the screw-on rear O2 sensor.

With a brand new cat though, I would think that the rear O2 sensor would be fine for some time. My recent emissions report was literally 0 in all three with a new single cat.

Since he doesn't have emissions testing, a rear O2 simulator could take care of any codes that pop up down the road...

oh thanks, I forgot all about the thread of the O2 simulator.

I hear the URD one works great.

Going by Walker Exhaust's lookup the '01-'02 are dual cat regardless of emissions standards, they do have different listings for Federal and California. See attached diagram.

Drew's right about the '00 Federal cat having a different flange than the CA.

If it seems to be running ok I'd try an O2 simulator or spacer (two spark plug defoulers). I'm going to try the spacer myself; just got a pending 420 code on mine but appears to be running normally.

oops forgot to attach the image...

Attached Images

 

In '01 and '02 the emissions standards for Federal and California are exactly the same and are indeed dual cat. The reason for the different parts listings is aftermarket parts in sold in California must be specifically approved by CARB (California Air Resources Board). The Federal parts are built to the same standards but have not been through the CARB approval process.

thanks all. grabbed the used early single cat system and will put it on this spring, too cold to mess with now. Also ordered a new Denso downstream sensor. will just live with check engine light and rattle for now.