The definition of the engine P0204 Code is Injector Circuit Malfunction – Cylinder 4. This problem of the car engine may occur for any of the causes from ECM is faulty, Open or shorted wiring harness, Failing cylinder 4 injector and Poor electrical connection. You need to check the engine well to know the real cause of the engine problem. You may check these symptoms, Poor fuel economy, Rich & lean conditions, Engine misfires, Lack of engine power, Poorly running engine and Engine that dies and will not restart to know the reason of the car engine problem. Do not drive this car until it get fixed.