I'm trying to find out which wire is the signal wire on 4 wire O2 sensors.
I know its one of the black ones, but if any one could tell me the color of the wire on the harness side, I'd be grateful.

I'd try to figure it out myself, but I'm not multimeter friendly, unfortunately...

BTW if it makes a diff, it's a stock D15 harness in a 92 Civ sedan (Exhaust Mani O2)

Tks

 

well from hours of taking off all the black tape off my engine harness this is what I found out:
primary o2 sensor
Black/Yellow = ground? well it goes to the Big cap that leads to nowhere
Black/WHite = sensor heater control
Green/black = ground? well it goes to the Big cap that leads to nowhere
White = primary heated o2, sensor -1

Secondary o2 sensor
Black/yellow = ground? well it goes to the Big cap that leads to nowhere
Black/white = sensor heater control
Red/yellow = sensor ground
White/red = secondary heated o2, sensor -2

 

Cool, Thanks a bunch!
Exactly what I needed to know !