Power to the O2 heaters or the sensors themselves?
The +12 v power to the O2 heaters is sourced by a 30 amp fuse that
goes through the contacts of the ASD relay.
There is joint connectors in the PDC..one is called Joint connect #2.
Ground for the heaters (02 sensors are 4 wire) is returned back to the
common ground point G103/G105/G107 there.
Sensor ground (the actual sensor itself, not the sensor heater) is sourced
at the PCM Connector C1 pin 4 , I believe.
(I have the pinouts for the 3 PCM connectors, handy).
The signal coming in from the sensors is read at the PCM, connector C1 (upstream) and pin 25 (downstream) .
Yes, there are intermediate connectors/jumpers/splices in the PDC which
make it a bit more difficult to trace.
S= Splice C=connector
Sensor ground is via S101, S103 to the upstream sensor,
and C106, S157,C352,S149, to the downstream sensor , and then C352 and C106
back to C1 on the PCM.
Why they had to go that complicated route is anybody's guess.