The automobile dictionary meaning of the car engine P2078 Code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 2 is MFG – Manufacturer Specific. 0 is Fuel And Air Metering. 7 for Vehicle Speed Output Circuit and 8 for PCM Stack Overrun. Do not drive the car with the car engine problem and you may face different problems in the car engine if the meaning of the code does not match with your car engine problem. That is why, find the real meaning of the car engine code and fix the car engine according to proper meaning of the code.