I live where I don't need to get a smog test for my registration. If I replace my cat with a straight pipe, what will be the impact on my after-cat O2 sensor? I don't want to get a bunch of codes telling me what a bad boy I am. I'm married.

 

lol.. i believe you should be fine.. we did the same to my friends truck and his is fine..

 

just be sure to make them test pipes where your cats usto be so if any codes pop up you could put your cats back on.,.

 

if you take it off...you'll need to get the back O2 sensors turned off via custom tune

 

Pull the sensor out then take some heavy guage wire and tie the tip to the exhaust pipe. The computer will still get the same even signal that it should. If you just let it hang it will never get up to temp.

Also if you ever get a smog test, I never said that.

 

^^ Don't think that works, it's a o2 sensor, not a thermometer.. But they sell o2 simulators online for like $20 or so. That or a custom tune is the only for sure ways to keep error codes away.

 

The rear O2 sensor checks if the cat is working or not. If the cat is working it will get a nice even signal. If the cat is not working it will get a signal about the same as the upstream O2 sensor showing that the cat is not working. If you put the down stream O2 sensor out in the open air it still shows a even signal. The only thing with just pulling the sensor and letting it hang is that the ecm also moniters the sensors temp to make sure that the sensor's heater is working correctly.

 

this method worked for my 97 bmw 540i for over 2 years until the elements destroyed the sensors and they threw a code. If you could find a way to protect the end of the sensors, you would be ok.