The problem of the car engine can be fixed easily if the meaning of the engine P0804 Code is found from online. The automobile dictionary meaning of the code is found online for free. You can learn general information from the automobile dictionary meaning and it is p for Powertrain Code Problem is related engine, transmission and emissions systems. 0 for SAE – Generic. 8 for Ignition System Or Misfire. 0 for IC Circuit High Voltage and 4 for Cruise Vehicle Speed/Set Speed Difference Too High. Do not drive the car until the car is tested. When the car engine is ok, then take it for a drive.