The general meaning of the code is important but not so important like the real meaning. The automobile dictionary meaning of the car engine P2121 Code has real meaning and the real meaning is found the car manufacturer. The engine should be fixed by an automobile engineer and the automobile dictionary meaning of the code can be used when it is necessary. The automobile dictionary meaning of the 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 1 for TFP Valve Position Switch-Drive Without Drive Ratio.