[fabriziobondi]

Problem: Passenger can switch on or switch off the engine.

Request: I would that only the driver can do this. Someone have a solution? Thank you.

[IceCube!]

if(GetPlayerState(playerid) != PLAYER_STATE_DRIVER) return SendClinetMessage(playerid, COLOR, "Error: You must be the driver to start the engine");

Use this or post your code.