rear heated O2 sensor location

[sporty25]

I have a 1996 240sx 5sp that needs a new rear heated oxygen sensor. I can't seem to find where it is located under my car. I have found two toward the front of the car, one under the hood near the engine and another on the exhaust pipe near the front drivers side wheel. How many O2 sensors are on my car? I have tried contacted the dealership, but they didn't even know. Somewhere their must be a book that tells people this. Any help would be appreciated. Thanks

[corn322]

there are only two from what I understand. one before the cat convertor and one after it.

so the one near the driver wheel is it.