O2 sensors?

[express_wagon]

Not an E34 specific question but kind of general, how many O2 sensors does a typical 4cyl (2000 Nissan Altima to be more specific) car have anyways?

I always thought it was somewhere b/w 2-3?

Thanks.

[Rus]

Modern cars typically have two O2 sensors. One is located before the catalytic converter and another is behind it.

[Bill R.]

2 o2 sensors both heated. A number of newer cars have 4 or more, the purpose of the rear sensor is to monitor the catalytic converter and verify that its doing its job.

Not an E34 specific question but kind of general, how many O2 sensors does a typical 4cyl (2000 Nissan Altima to be more specific) car have anyways?

I always thought it was somewhere b/w 2-3?

Thanks.