Patent ID: 6615778
Filing Date: 2003-09-09
Classification: F01L

Abstract:
An apparatus for diagnosing a variable valve timing apparatus comprising:a variable valve timing apparatus which comprises, a camshaft for driving an intake valve and an exhaust valve of an internal combustion engine to be open/close, a valve timing adjustment mechanism for variably controlling a rotation phase of said camshaft with respect to a crankshaft, to adjust the valve timing of said intake valve and exhaust valve; a change amount calculation unit for calculating a change amount per unit time in a control target value of said rotation phase; a comparison unit for comparing said calculated change amount with a predetermined limit value; a diagnosis permission unit for permitting an abnormality diagnosis of said variable valve timing apparatus on a condition that said change amount has been kept equal to or less than said predetermined limit value for a predetermined period by said comparison of said comparison unit; and a diagnosis unit for diagnosing an abnormality of said variable valve timing apparatus when said diagnosis permission unit permits said abnormality diagnosis.