[Lajko1]

pawn Код:

public OnPlayerStateChange(playerid, newstate, oldstate)
{
    if((newstate==PLAYER_STATE_DRIVER)||(newstate==PLAYER_STATE_PASSENGER))
    {
      new CarsNames = GetPlayerVehicleID(playerid);
      new Model = (GetVehicleModel(CarsNames))-400;
      new str[50];
      format(str,sizeof (str),"%s",CarsNames[Model]);
      GameTextForPlayer(playerid, str, 5000, 1);
    } return 1;
}

You are using this function on callback where "vehicleid" is not defined
I'm not sure if code that I gave you work, but give it a try

Also you have 2x "new CarsNames" change one of them to different name..