The automobile dictionary meaning of the car engine P2125 Code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 2 for MFG – Manufacturer Specific. 1 for Transmission. 2 for Air Conditioning (A/C) Clutch Feedback Circuit High Voltage and 5 for Park/Neutral Position Switch Circuit Engine Torque Signal Circuit. Deactivation process of the engine cylinders is achieved by freeing a synchronizer pin that generally interlocks the cam follower and rocker arms. The engine P2125 code resolutions the synchronizer pin what is released using hydraulic heaviness which is controlled by a dedicated solenoid. The car engine should fixed by an automobile engineer.