jkJackswfl

I have a 2012 JK with 85k miles. My check engine light came on and the code was PO137 which said my O2 sensor bank 1 sensor 2 was bad. I was told that bank 1 was the drivers side so I replaced the sensor downstream of the cat. I cleared the code and now it keeps returning. I checked the connection and its good. I find that if I clear the code and then drive the vehicle for any amount of miles 0-500 for example the light and code will not reappear until I turn off the ignition and restart. Sometimes right away and sometimes after 2-3 starts. Can anyone shed any light on this? Thanks for your help.