I was hookin up a Air fuel gauge and i just wanted to make sure i did this **** right..... on the harness for the O2 sensorthere is 4 wires (2 white, black and gray), could someone just confirm which one was the signal wire. Thanks a ton.

 

what kind of guage is it

 

its a autometer, the signal wire on it is purple, but i was just wonderin what color the signal wire on the 02 sensor is, not the gauge