That device is the evaporative emissions system Purge Solenoid. It operates on a pulse width modulated output from the PCM. The ticking clock type noises it makes are normally heard as the vehicle is warming up. The noise can be bothersome to some people, as it may be audable from inside the Jeep. If it is, you can add a second rubber isolator to it's mount, something I used to do regularly as a Jeep Dealer tech.