GM Delphi / Packard - Gray Female O2 sensor connector with 5 pins (1 blocked) + TPA + CPA. Perfect for O2 sensor extenders, simulators, etc.
TPA = Terminal Position Assurance, prevents terminals from backing out of connector
CPA = Connector Position Assurance, prevents connectors from coming loose from one another. This is a special CPA made for this type of application, remember to put the "loop" part of this cpa around the wires to prevent the CPA from being lost when you are disconnecting or connecting the connectors from one another.