You can use automobile dictionary meaning of the engine P1504 Code when you need to fix the car engine but you look for the real meaning of the code first. Do not use any other meaning of the code first. The automobile dictionary meaning is general meaning and you can use this meaning if the real meaning of the code is not found. 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. 5 for Computer And Auxiliary Outputs .0 for IC Circuit High Voltage and 4 for Cruise Vehicle Speed/Set Speed Difference Too High.