So I'm extending my O2 sensor to a side exit header I just got. I start cutting and splicing the wires and then realize I have two black wires that are exactly identical. By the way its a 4-wire O2 sensor. What I'd like to know is if it matters which black goes to which black. I feel like an idiot for not labeling them first so if anybody knows if it matters or how I can distinguish between the 2 please let me know. Thanks

 

The two black wires are ground. It makes no difference which way you connect them. You can relax...

 

If thats the case then cool dude. Thanks for the help