The engine system, in conjunction with the engine control module or powertrain control module, activates the engine P0144 code solenoid valve to switch oil compression to the engine mechanism that is fit in the valve system to switch valve timing between Low and High. If the engine solenoid valve has a short circuit or open, a DTC is stored. The oxygen 2 sensors on your car amount the oxygen in the finish to determine how rich or lean the ratio of fuel and air are in the cylinders. Enhancing this combination means better fuel cheap and fewer use releases. A test drive is recommended once the car engine is fixed.