The automobile dictionary meaning of the engine code is not very important but it is suitable when the right meaning of the code is not found. The automobile dictionary meaning of the car engine P1815 Code is found online and it is p for Powertrain Code Problem is related engine, transmission and emissions systems. 1 for MFG – Manufacturer Specific 8 Ignition System Or Misfire. 1 for Low Coolant Circuit and 5 for Park/Neutral Position (PNP) Switch Circuit Engine Torque Signal Circuit. Here the powertrain is the main problem and this problem can be fixed fast and easily. Do not use wrong meaning to solve the car engine.