Hey All. I am looking for a bit of help finding where the power supply to both my O2 sensors comes from. I have had some rough running for a while now and discovered today that neither probes have a power supply to them. I checked both connections on the wiring harness that correspond to the white wires on the sensors with ignition on and then engine running. I seem to be getting the correct reading from the probe signal wires, and I have nearly no resistance across the heater wires. Does this mean the sensors are shorting? As far as I can tell the power supply wires in the harness go direct to the ecu but I'm not sure if there is a relay before this or even a fuse. All advice greatly appreciated.