02 sensor wires what do they mean
 

hello i am trying to find out if anyone knows what the 4 o2 sensor mean, i havean aerio 2003 sx. there is a black grey and 2 white wires i am looking for specifics as to which is signal input to ecm, i know to of the wires are to the sensor heater and one is signal out put and siganl return to ecm any help would be greatly appreciated thanks Dean.