Chrysler Pacifica Owner's Manual page 346

346 STARTING AND OPERATING
The Trailer Tow Package may include a 4 and 7 pin
wiring harness. Use a factory approved trailer harness
and connector.
NOTE: Do not cut or splice wiring into the vehicles
wiring harness.
The electrical connections are all complete to the vehicle
but you must mate the harness to a trailer connector.
Refer to the following illustrations.
4 - Pin Connector