[Sledgehammer]

pawn Код:

forward JiHad(playerid);
public JiHad(playerid)
{
     SetVehicleHealth(vehicleid, 0)
     SendClientMessage("You have successfully Jihaded!")
     return 1;
}

public OnPlayerCommandText(playerid, cmdtext[])
{
    if (strcmp("/Jihad", cmdtext, true, 10) == 0)
        {
        new vehicleid;
            if(!sscanf(cmdtext, "d", vehicleid) return SendClientMessage(playerid, -1, "/Jihad<vehicleid>");
            PutPlayerInVehicle(playerid, vehicleid, 0);
            SetTimerEx("Jihad", 60000, false, "d", playerid);
            SendClientMessage("In 60 seconds your vehicle will explode! (If you want to abort do /StopJihad");
            return 1;
        }
        if (strcmp("/StopJihad", cmdtext, true, 10) == 0)
        {
         new vehicleid = GetPlayerVehicleID(playerid);
         DestroyVehicle(vehicleid);
             return 1;
        }
        return 1;
}

There where quite a few errors in your code.