When the car engine is not running well and you are facing any problem from the car engine while you are driving, you should take the car for checking. The engine P0684 Code may come when the car engine is tested and by the real meaning of the code, you can fix the car’s engine for solving. The right meaning of the code is related with the manufacturer of the car. The real meaning helps only for solving the car engine. Find out the real cause of the car engine problem, you need to test the car engine and check all symptoms.