You are right,anything after 99 uses a networked system that really should not be tampered with. Your XC-90 needs a confirmation from the central electrical module that the key is accepted to the engine control module that then enables a relay to make the starter work and o.k.s the fuel pump and spark to start the car. I am not saying that it cannot be done but I could tell you horror stories about cars that aftermarket accessories have been installed where the part is not compatible and or the installer used the wrong wire.