The engine P0503 Code is found in all car engines only and you should rely on the real meaning of the code. The meaning of the code helps only for solving the car engine. The engine code is very informative what contains many information for solving the car engine properly. Solve the car engine as you know the meaning of the engine code. Check the car engine and find all possible problems of the car engine. Once you know the problem of the car engine, you should fix the car engine and make sure that the engine is purely ok for your safe driving.