O2 Sensors ???

[ryan34]

I believe there are 4 oxygen sensors, i need to know what they do. I also need to know the order, and is that standard on all cars(federal mandate)? I ask because i have a friend who is going catless on his dakota R/T and has a o2 sensor replacement and we need to know which one it replaces. Thanks for any advice

[Benm109]

All '96 and later (OBD II) cars have 4 oxygen sensors, IIRC. I don't think there is any set order for them. You only need two oxygen sensor simulators (I am assuming that is what you're talking about) for the rear (after the catalytic converter) sensors. The fronts are used to measure how the engine's running while the rears measure the efficiency of the cats (in layman's terms), so the rear are all that need simulators.

[ryan34]

Yeah, we have the simulater. So the only one we need to replace is the one after the cat? And what about the one inside the cat? He is going to gut the cat.