Üdv áthoztam nektek a kódot a hivatalos fórumról.
Eredeti téma link: http://forum.sa-mp.com/showthread.php?t=348336
 

if (strcmp(\"/siren\", cmdtext, true, 10) == 0)
{
        new objectid = CreateObject(19419, 0, 0, 0, 0, 0, 0);
AttachObjectToVehicle(objectid, GetPlayerVehicleID(playerid), 0.009999, -0.019999, 0.944999, 0.000000, 0.000000, 0.000000); //Object Model: 19419 |
SendClientMessage(playerid, COLOR_RED, \"You\'ve Added a siren to your vehicle\");
return 1;
}