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 making a fault determination while preventing an erroneous determination even at low oil temperatures. The variable valve timing mechanism is driven by an oil pressure of a working oil 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 to change an opening/closing timing of the intake valve and/or exhaust valve, and to control the actual cam phase in a feedback manner to reach a set target cam phase. The fault determining apparatus comprises a fault determining routine executed by an ECU for determining that the variable valve timing 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.