The engine P204D Code is necessary thing and the general meaning of the code is not very important thing. The automobile meaning of the engine is p for Powertrain Code – Problem is related engine, transmission and emissions systems. 2 for MFG – Manufacturer Specific. 0 for Transmission. 4 for Control Module Throttle Actuator Position Performance and D for TFP Valve Position Switch-Drive Without Drive Ratio. The engine code P204D OBD2 precisely refers to the camshaft (cam) timing. In this case, if the cam timing is over slow, the engine light will be illumined and the code will be set.