O2 sensors in I6 4.9 liter
 

New to Ford trucks and this forum, just got a nice 96 F150, I got CEL and it is one of the O2 sensors, something about the "heating circuit" in one, stupid me erased the code but I'm sure it will come back soon, although maybe not, the thing runs great. Anyway there are "banks" and sensor numbers. Anyone know which one is which (total of three, two in the manifold and one post cat I believe), are all these the same type sensor. Are the four wire leads power, signal to computer, ground, and what would the other be, signal ground? Are there separate fuses and relays for these sensors, nothing in the fuse panel I can see. I read that many sensors don't use heaters that are near the head because they get hot enough, so i wonder if it detects a heater malfunction but still does its job anyway. Ya, got a lot of questions but I love this truck and like the idea of a big displacement inline six and want to keep it running tip top, thanks

B1S1 is bank 1, which is the group of cylinders corresponding to the #1 cylinder designation, sensor 1, which is the "upstream" sensor or the sensor closest to the engine. This is the fueling sensor.

B1S2, is bank 1, sensor 2 or the "downstream" sensor, or the sensor that monitors the catalyst performance.

B2S1, as you should now guess, is bank 2, the bank without #1 cylinder in it, sensor 1. IF you had B2S2 it would be the down stream sensor for that banks catalytic converter.

Also, you posted in the Performance F150 section for the high performance trucks. Since you have the 300-6 cyl this probably isn't the best forum for you.