OK, you shouldnt cut the wires going to an o2, the ecu is calibrated for the car and its set up for the number of connections that car should have, each connection is a slight voltage loss and since you are only dealing with about 1 volt max, it could get it out of whack, The o2 sensor isnt what goes closed loop, the ecu is, and that happens after a number of things happen, like the coolant temp reaches a certain degree, and a timer runs out, and the o2 goes past .5 volt,. but i have seen the ecu get tired of waiting for the o2 and just go closed loop anyways and maybe throw a o2 lean code. Some car makers make a generic program that will work with several motors, you will notice wierd things like no injector pulse width for bank 2, no mass air reading, but the map reading is there, no reading for the b2s1 o2 when its a 4 cyl with 1 bank and 2 sensors, one upstream and 1 downstream, junk like that
. You should have a sensor for each head in obd2 and at least 1 downstream, but i have seen exceptions
If your upstream never goes past .5 volt even if you floor it, you could have a dead sensor or a heater in the sensor thats not getting voltage
You really should find somebody with a snap on or good scanner and knows what their doing to give you a heads up on all the o2 sensors and what they are reading during driving
"Skoolin' the unlearned!"
It worked fine until I fixed it! 
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