Hey guys I'm at my wits end , I bought an aftermarket O2 sensor Upstream . it was defective but it plugged into the harness just fine , had to send it back . then the new one arrives ,I test it ,it's good ,I install it , then I go to plug it in and it won't go all the way in ,so after fighting it for 30 minutes , I go cut the old harness off and tried to plug it in , it won't go on . There are little plastic stops on the harness side that stick out farther than the prongs ,so it never makes electrical contact. Did these stops grow there while I was working on the rest of the car? The downstream O2 sensor went right in.