Possible causes

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

When is the code detected?

After the ECM sends the target duty cycle 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 duty cycle ratio varies from the target duty cycle ratio.

Symptoms

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

P0021 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.