The powertrain problem can be fixed easily and the car engine P1781 Code is found from the car engine by the test. However, the car engine may make several problems if the problem is not solved. Every part of the automobile engine code is meaningful. The automobile dictionary meaning of the engine code is found online and it is p for Powertrain Code Problem is related engine, transmission and emissions systems. 1 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.