The powertrain problem of the car engine is not difficult thing. This problem is cheaper and easier to solve. The engine P2421 Code is found in the car engine and it is related to the problematic area of the car engine. So, when you get the code, it becomes easier to know the problem and fix the car engine problem. As the problem is found in the powertrain, It can be fixed fast by an automobile engineer quick. Do not allow any immature person for solving the car engine problem. When the car engine is ok, take it for a test drive.