Check engine light came on and checked code and it is p0139 02 sensor ckt slow on 2007 Honda Accord

Bank 1 sensor 2 please help

Asked by for the 2007 Honda Accord
Either have a shop CONFIRM the O2 sensors function(or lack of) , because certain other causes are possible (though unlikely), OR replace sensor. 4cyl. - second sensor , 6cyl. rear bank second sensor (between firewall and engine)
I have the 4cy. Which and locating of this sensor? Thanks
It's the second sensor.