The car engine P2781 Code has several meanings and the most suitable meaning of the car engine code is found in the car engine manual what is provided by the car manufacturer. You may use the general meaning of the car engine code for solving the car engine problem. The general meaning of this car engine code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 2 for MFG – Manufacturer Specific. 7 for Auxiliary Emission Controls. 8 for Exhaust Gas Recirculation System Valve 1 and 1 for TFP Valve Position Switch-Drive Without Drive Ratio. But you should try to use the real meaning of the code.