- Dirty Oil
- Variable Valve Timing (VVT) sensor circuit is open or shorted
- Variable Valve Timing (VVT) sensor poor electrical connection
- Faulty Variable Valve Timing (VVT) sensor
- Damaged ECM

There is a factory service bulletin for following Scion models.


2005-2006 Scion xA
2006-2006 Scion xB


Scion Service Bulletin OBDII Code P0016

The Engine Control Module (ECM) set code P0016 when no receives no signal from the Variable Valve Timing (VVT) sensor.

- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of power
- Engine rough idle

The Engine Control Module (ECM) controls the Oil Control Valve (OCV) to regulate the intake camshaft angle. As a result of the angle change, the engine timing is advance or retard. Optimizing engine timing will help the engine improve torque and fuel economy, and the exhaust emissions decrease under overall driving conditions. The Variable Valve Timing (VVT) system includes the Oil Control Valve (OCV) and VVT controller. The ECM detects the actual intake valve timing using signals from the camshaft and crankshaft position sensors, and performs feedback control.