Ficou assim

new vehicleid, engine, lights, alarm, doors, bonnet, boot, objective;
    if ((newkeys & KEY_YES) ** !(oldkeys & KEY_YES))
    {
        if(IsPlayerInAnyVehicle(playerid))
        {
            if(GetPlayerState(playerid) == PLAYER_STATE_DRIVER)
            {
                GetVehicleParamsEx(vehicleid, engine, lights, alarm, doors, bonnet, boot, objective);
                if(lights == 0)
                {
                    SetVehicleParamsEx(vehicleid, engine, 0, alarm, doors, bonnet, boot, objective);
                }
                else
                {
                    SetVehicleParamsEx(vehicleid, engine, 1, alarm, doors, bonnet, boot, objective);
                }
            }
        }
        return 1;
    }