The O2 wires use the same powers and grounds used in the transmission harness so you need to inspect the harness to the trans, over the trans and to each of the 4 O2's. You need to look for wire chaffs. Here is a wire diagram to see the wire color connection
On both sides of the transmission are the left and right bank exhaust. The O2 are in there and the harness will be very visible once there. There is not a general area of wire chaffs. I would begin by looking at the O2 wires burning on the exhaust.