DTC P0078, P0084: EVT Control Solenoid Valve: Description
WARNING: This page is about a different car, the 2011 Infiniti FX50. However, it is still accessible from the selected car via links, so may be relevant.
Exhaust valve timing control solenoid valve is activated by ON/OFF pulse duty (ratio) signals from the ECM.
The exhaust valve timing control solenoid valve changes the oil amount and direction of flow through exhaust valve timing control unit or stops oil flow.
The longer pulse width retards valve angle.
The shorter pulse width advances valve angle.
When ON and OFF pulse widths become equal, the solenoid valve stops oil pressure flow to fix the exhaust valve angle at the control position.