CJB is your Central Junction Box. Its also known as PJB (Passenger Junction Box) or BCM (Body Control Module). It requires reconfiguring to tell it, its going towing electrics. This is requires as when you fit towing electrics to a FL2, you install a trailer module behind the n/s/r quarter panel. You need to tell the CJB to communicate with it. If non-genuine towing electrics are fitted, then this can vary in compatibility. It depends how functional the module fitted is in simulating the geniune Trailer Module.
The PDC is just Park Distance Control. Tis the bleeping you might get when reversing into walls if fitted.