The powertrain problem of the car engine is faulty and it needs to fix. The engine P0400 Code gives some general idea about the car engine problem. If you follow the right meaning of the code, you have hand tools and you have experience for solving the car engine, you can fix the car. You do not need to worry about it if you do not know how to solve the car engine. You should ask help from the automobile engineer for solving the car engine problem. However, do not drive the car with the car with the engine problem.