You should always accept the right meaning of the car engine P1503 Code for solving problem from your car engine. If you do not know the real meaning, you can use automobile dictionary meaning what is easy to find. The automobile dictionary meaning of the car engine code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 1 for MFG – Manufacturer Specific. 5 for Computer And Auxiliary Outputs. 0 for IC Circuit High Voltage and 3 for Transmission Control Module Reprogrammable Memory. Do not use this meaning of the code for solving the car engine if you know the real meaning of the code.