O2 sensor faults even after changing sensors

was having O2 sensor faults, regularly, bank 1 sensors. Replace both sensors, checked for cracks and leaks, from header all the way down, all good. Still get O2 fault, it changed to bank 1, position 1. Decide to test old sensors, heater ohm ok, voltage come up and drops off after heat removed. Anyone know what's going on with this thing. After changing sensors, it improved to 50-50 chance it will or not come on. If it starts and light doesn't come on, I can drive 20 or 200 miles, and it stays off. next time, I start may or may not come on. Hello I don't get it. Next I will unplug sensors and at least check the heaters.

 

For the vehicles in my fleet I prefer OEM O2 sensors whenever possible for best results.

 

Up date on 02 sensors. Changed both sensors on Number 1-bank. Still shows upper sensor bad. Bought another sensor different brand. problem solved. New parts, doesn't always mean good.