are you swaping this in a truck or older rig??? that connector is for the FUEL COMPOSITION SENSOR. the wiring harness you are working with is a L59 flex fuel engine harness. designe to operate on high concentration of ethanol alcohol fuel, have you heard of the new E85 fuel??? that is it.... the connector pin A = white, fuel temperature compomposition signal... pin B = pink, ignition 1 voltage... pin c = black, ground....... if you have the complete engine you will need the matching fuel pump, injectors, fuel comp/temp sensor for it to work correctly. the L59 engine designed on E85 fuel has a fuel system that flows 50% more fuel than a regular system. its differnet but not bad. you just need to keep that in mind when tuning it. the engine computer needs to know how much ethanol is in the tank to make the engine run correctly, it takes as muck as 50% more alcohol to operate the engine correctly compaired to gas. the system is intergrated into the fuel tank system and keeps tabs on fillups. not quite sure excactly how though. i do know that you can have all that turned off and make to just a regular engine,,, just keep in mind of the high flow rate injectors adn fuel pump. (food for thought....when installing a magnacharger radix on a L59 flex fuel suburban, you swap over the old injectors, and can never fill up with more than 10% ethanol fuels. thats how much extra they flow. pluss i think they have diferent connectors)