The car engine should be checked for identifying the problem and find the right solution of the car engine. The engine P1840 Code is set in the car engine and meaning of the code is necessary to use for solving the problem. The engine code’s meaning identify the real cause of the car engine problem and helps to fix the car engine. The letter P means powertrain and this problem is not very difficult to solve. Once the car engine is fixed, you can drive the car engine but you should confirm that the car engine is ok and it is possible by a test drive.