P3 infotainment comes in tiers. The audio module (the IAM — Infotainment Audio Module) ships at a level that matches whatever the car was optioned with, and the higher tiers unlock things the base cars simply don't have: the RTI / Sensus navigation menus, and on this generation, rear-seat DVD. The hardware is often physically similar; the difference is the module level and what the car is configured to expect.
This upgrade went for the top of the S60's tree — a Level 3 IAM 2.1 with navigation and DVD. That means the right head unit, the GPS antenna and its feed, the screen, and the wiring to carry it. The infotainment harness is its own branch in the parts catalogue for a reason: audio tier, telephone, navigation and DVD each change what runs behind the dash, which is exactly why a generic 'S60 head unit' off a shelf so often does nothing when you plug it in.
Getting the parts in is half the battle. The other half — the half that separates a working nav from an expensive paperweight — is CarConfig. The car has to be told it now has navigation, that the DVD source exists, that the menus should appear. Those are configuration parameters in the modules, edited with a P3 config tool. Flip the right values and the nav menu appears, the map draws, the DVD becomes a selectable source. Miss them and you have a very heavy, very silent upgrade.
That's the whole thesis of working on these cars: the capability is usually already in the platform, waiting behind a configuration byte. Fit the factory part, wire it the way the factory would, then tell the car the truth about itself. The album walks through the module, the wiring and the config screens.