searched but no real answer (o2 sensor question)

[ceniack]

will removing the o2 sensor after the cat effect engine performance? or is it just there to say that the cat is working correctly and throw a CEL if it isn't.

[NISTECH]

The rear o2 is for cat moniter only on 95 and newer nissans. some not till 96. It has no effect on fuel control unless the front goes completely dead and even then it does do much for control since the cat effects what it sees. What year and model is the car your working on?

[ceniack]

well, i'm not really working on a car, i am just having a debate with a friend of mine that is trying to tell me that if you take off the cat, you have to get an o2 simulator or the car will run like crap, and i was trying to tell him that it wasn't the case on nissans (he drives a BMW though) but that i wasn't sure about other cars.

thanks for the help though

[NISTECH]

The rear O2 is a federally mandated device for cat moniter. When a cat is functioning properly the rear O2's reading is not accurate enough or with in a range that is suffecient for engine control. Therefore it can not be used for fuel management as it would cause the car to run poorly if it was used. The simulator is a good idea to prevent CEL illumination though. This applies to all OBDII vehicles. A note though for your buddy if he is planning on removing his cat he needs to be aware BMW uses a heated cat on many of their models. It is set up to throw a code if it doesnt see a specific amperage or voltage drop on the circuit when it activates the cat. This will also not only throw a code but if it will also have a Heated cat moniter if the codes are cleared that moniter still needs to be ran to pass an emission inspection in many states. Once the moniter runs it will throw the code.

[ceniack]

we settled the debate, lol.

thanks for taking the tme to answer.