The engine P266D Code lets you know about the engine problem and follow the right meaning of the code for solving the car engine. The general meaning of the code is not helpful always. You can learn the automobile dictionary meaning of the code for getting knowledge. Those symptoms are decreased engine performance and increased fuel consumption found on the car engine when the car engine is tested. You should find cause of the car engine problem and find the problems of the car engine from the car engine diagnosis. All those problems are powertrain Control Module (PCM) failure, Variable valve lift controller assembly failure and wiring issue.