Fault determining apparatus, fault determining method and engine control unit for variable valve timing mechanism

摘要

A fault determining apparatus for a variable valve timing mechanism is provided for shortly and accurately determining a fault even at low oil temperatures. The mechanism is driven by an oil pressure to change a cam phase of an intake cam and/or an exhaust cam with respect to a crank shaft of an internal combustion engine, thereby controlling the actual cam phase to reach a target cam phase. The apparatus has a fault determining routine executed by an ECU (electric control unit) for determining that the mechanism is faulty when a cam phase difference between the target cam phase and the actual cam phase is not within a predetermined range, an oil temperature sensor for detecting the temperature of the working oil, and a correcting routine executed by the ECU for correcting the predetermined range in an increasing direction when the detected oil temperature is low.