2001 O2 sensor wiring?

[Heavy hitter]

I know the 2 white wires on the rear o2 sensors are the heater wires. But which of the black and grey is positive and negative? As far as I can tell gray might be negative? Anyone know?

[smj999smj]

The wiring diagrams go by the wire colors of the main harness, not by the wire colors on the subharness of the O2 sensor, itself. Wiring diagrams for the O2 sensors can be found in the Engine Control section of the factory service manual. If you register to NissanHelp.com, you can get a free download of the EC chapter for your vehicle here:

https://x.nissanhelp.com/forums/Knowledgebase/links/70/

Or, you can get a full service manual access at Nico Club's site.