The engine code’s real meaning is the most important thing. You can find the real meaning of the engine P1788 Code from the manufacturer of the car engine manual but the meaning of the code is sufficient, then you can depend on the automobile dictionary meaning and it is found online easily. The automobile dictionary meaning of the code 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 8 for PCM Stack Overrun. However, take the car for a test drive.