New Pathfinder Owner needs help

[trucker185]

Hi Everyone
Not a great way to start out as a new pathfinder owner but i have a problem with my pathfinder.I have a 2005 t-spec pathfinder with the sat nav unit under the drivers seat.Neither the sat nav,radio,cd seem to work.When i start the car up the screen comes on for a few seconds and then goes off along with the radio.It continues to do this switches on and off.I have tried a new screen but it still does the same.
Has anyone got any ideas as to what could be the problem before i go to Nissan??
Any help much appreciated