My O2 sensor wires were ripped out of their plug so I'm splicing a new one in (Vehicle side..not the sensor side). Anyway...the plug is a 4 wire, but there is a black wire that I'm not sure where it goes. Can someone tell me where this is supposed to connect to? It's in the same bundle of wires that dump out to the O2 sensor's plug, but the plug itself has 4 going to it and nowhere for the black wire. ??