Possible causes

– Dirty or low engine oil
– Faulty variable valve timing (VVT)
– Faulty oil control valve (OCV)
– Variable Valve Timing (VVT) harness is open or shorted
– Oil Control Valve (OCV) harness circuit is open or shorted
– Damaged ECM

Tech notes

There is a factory service bulletin for following Scion models.

2005-2006 Scion xA
2006-2006 Scion xB
Scion Factory Service Bulletin OBDII Code P0012

When is the code detected?

After the ECM sends the target dutyandcycle signal to the OCV, the ECM monitors the OCV current to establish an actual duty cycle. The ECM determines the existence of a malfunction and sets the DTC when the actual dutyandcycle ratio varies from the target dutyandcycle ratio.

Symptoms

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

P0012 SCION Description

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.