Removing rear catalytic converter, legal?
 

I have a Cali spec, with 2 catalytic converters. It's throwing P0420, and it's not the sensor. The converters are old and rusty and need to be replaced. The whole exhaust is rusty and needs to go (except headers).

So, would ordering an aftermarket non-California bolt on exhaust be ok in Pennsylvania?:hillbill:

It is illegal under Federal law to change the original characteristics of the emissions control system no matter where you operate the truck. It will also probably not satisfy your ECM; you will be looking at a pretty yellow light forever (unless you get a sim).

That said, anything further depends on what emissions testing you have in your part of PA. If there is none, nobody will ever know and you will be OK until you try and sell that truck with a pesky yellow light. If there is, you better stick to a Cali. system that is able to keep that light off--or get a sim. Walker does make an aftermarket Cali. system if you want to try that route.

That's it! I'm joining the Lemon Party. I mean the Tea Party. EPA needs to go! :hillbill:

Now, the interesting thing is after reading some rules, it seems the catalytic converter has to be documented as bad, by an inspection station or mechanic. Replacing it for no good reason seems to be illegal.

And it seems they don't want DIY. Is it a gray territory and a DIY bolt on Walker job is just fine?

There are a LOT of laws like that but no one follows them. You can go to any exhaust shop and have them swap out cats as much as you want.

Now technically yes it is illegal to remove any cat but depending on your emission testing you can usually get away with it.

Here on OBDII cars all they do is plug into the ECU and if there are no codes you pass. Makes it a piece of cake to pass without a cat.

In my case i gutted my stock cat so it passes visual inspection. Then made up an O2 simulator with radio shack parts for $15 and i have been good ever since. No codes, no problems passing inspection and some free power to boot.

If you search my old posts i link to the O2 simulator i built.

Couldnt you say they were
 

stolen?

If it came down to that, I probably could. :hillbill:

Texas_Ace: is your truck Cali emission? I'm wondering if that capacitor/resistor mod will work on a Cali model.

Out of curiosity, are the ECM programming metrics for the exhaust any different between cali and 49-state vehicles? do the Cali vehicles have higher standards for the CEL light than 49-state ones?

It should work fine. The cali models have a wideband front O2 sensor but the rear sensor (the one that checks if the cat is working) is still a narrowband IIRC.

If it is a narrow band then that should work fine as it is pretty universal.

Texas_Ace: I might go that route then and just keep the current exhaust until it falls off from rust.

What values for the capacitor and resistor did you use on your 3rd gen?

I did the trick outlined in this post: https://www.yotatech.com/50697664-post28.html

Using this schematic: http://www.vfaq.com/mods/O2bypass.html

Worked great, been 3 years and no issues.

too much work IMO, use the spark plug anti-fouler trick. Most shops won't even notice it.

I tried that and it would not work because our O2 sensors are a 2 bolt sensor not the screw in style.

hmmmm lol good point, I am surprised your the only one who mentioned that so far as I know I have brought that trick up a few times.

Soldering in a tiny resistor and a capacitor in is about as easy as it gets. :hillbill:

But the principle behind that adapter is basically taking the sensor further out of the exhaust flow. Isn't the rear O2 sensor just a temperature sensor? So in effect, a 'failing' catalytic converter runs hotter than a 'working' one.

What about the issue of bypassing the real O2 sensor, then having the catalytic converter plug up and glow red and set the car on fire?:scared:

It is easy, i made a separate box to hold all this stuff so it would be kept out of the weather but still only took me 10 mins to put it together.

The O2 sensor is not a temp sensor, you are thinking of an EGT sensor. It detects how much oxygen is in the air in a nut shell.

The front sensor is what the ECU uses to adjust the fueling so it stays at the right AFR (usually 14.7:1). The rear O2 sensor is then compared to the front sensor to determine if the cat is working.

The rear sensor should have a lower reading then the front sensor which is what the resistor and capacitor does. Just lowers the signal to make the ECU think that the cat is still there.

There are 2 kinds of O2 sensors, wideband and narrow band. Wideband allow you to see the exact AFR you are running at.

Narrow band sensor as basically a game of Hot/Cold. It only comes aline around 14.7:1. The ECU has to then fish around to find the right amount of fuel by trial and error.

Do a google search and you will find a ton more info on them. In a nut shell all that matters for us is that the rear sensor is a narrow band sensor and the above O2 simulator works great at fooling the ECU into thinking that the cat is still working.

Far as it clogging up and starting a fire, generally when it gets clogged you will lose massive amount of power. You will know if it gets clogged but it is a very rare thing to have happen on piston engines. Now Rotorays do it all the time but they still don't catch fire.

Texas_Ace: btw, where did you tap the wiring for this mod?

I tapped it into the O2 sensor side of the pigtail IIRC that way it was completely reversible with a new O2 sensor. The box itself was weather sealed with caulk/sealant and then zip-tied up under the truck by the O2 sensor. Worked great for over 3 years so far.

Texas_Ace, have you looked at your OBDII voltage readings after this mod?

I unplugged my rear O2, plugged in a 1uf cap + 1m ohm resistor, both running in parallel just like that diagram, and I'm showing 0 volts. Plugging in the real O2 returns the normal sinewave. :think:

I did indeed watch it on the OBDII scanner after i did it. Worked just as it should, same voltage spikes only smaller.

My guess is the problem lies in the wiring someplace. either used the wrong wires or something. I remember it took me a little while to figure out the wires to tap into. Had to get the wiring diagram from the dealer to figure it out.

It is weird indeed. I'm sure I got the wires right though (black+black=heater, white=ground, blue=signal). Tested the cap and resistor with a Fluke, both come out within 0.1%, so everything is good there too.:think: