This engine P1391 Code is an important and it has a meaning what is necessary to know. This engine code has various meanings and based on the car band, you will find the meaning of the code. The automobile dictionary meaning of the code can be used for all of the car engines but if the real meaning of the code is found, then it becomes easier to fix the car engine and solve the car engine properly. Do not use different meaning of the code what are provided by the different car brand. Do not drive the car for long drive what may make more trouble.