[Konstantinos]

525 is the modelid, you need to use the vehicleid and in that case, you should create the vehicle with a name and use that in the function.

pawn Код:

// Example:

// Global variable
new 
    mechanic_veh
;

// Somewhere you create the vehicle
mechanic_veh = CreateVehicle(525 ... /* rest of params */);

// to that command
if(!IsPlayerInVehicle(playerid, mechanic_veh)) return SendClientMessage(playerid, 0xE0313AFF, "(( [Mechanic] You are not in a mechanics vehicle! ))");

You should also check if he is driver to use the command, because he might be passenger.