The automobile dictionary meaning of the P0604 Code is p for Powertrain Code Problem is related engine, transmission and emissions systems. 0 for SAE – Generic. 6 for Vehicle Speed Control And Idle Control System. 0 for IC Circuit High Voltage and 4 for Cruise Vehicle Speed/Set Speed Difference Too High. Due to the false meaning of the code, the engine may get more terrible problems in the car engine. However, when you seek the car engine code meaning, you should know the right name of the car and manufacturer’s name. You should not fix the car engine by the inexpert automobile engineer.