Possible Causes

WARNING: This page is about a different car, the 2003 Infiniti G35. However, it is still accessible from the selected car via links, so may be relevant.

Malfunction is detected when there is a gap between angle of target and phase-control angle degree. Possible causes are:

Harness or connectors (IVTC solenoid valve circuit is open or shorted).
IVTC solenoid valve.
Crankshaft position sensor (POS).
Camshaft position sensor (PHASE).
Accumulation of debris to the signal pick-up portion of the camshaft.