2000 CHEV. Venture injector wiring harness

I am attempting to replace the injector wiring harness on this vehicle, however the coolant temp. Sender connection in the new harness has a three wire connector ;the original was a two wire, as is the sender. There is no connection in orginal main harness for the new third wire, so do I replace the two wire sender with a three wire?---Or cut new harness and install old two wire connection and use old sender. The local dealer unsure of what to do, they leaned toward use old connections. I don't want to make trouble for myself. I would appreciate the correct procedure in this case. THANKS IN ADVANCE