Patent ID: 6923150

Claim:
A valve timing control system for an internal combustion engine, comprising: crank angle detection means for generating a crank angle position signal corresponding to a rotational angle of a crank shaft in an internal combustion engine; cam angle modifying means for modifying at least a relative position of a crank shaft and a cam shaft for one of air intake and gas exhaust; cam angle detecting means for detecting a cam angle modified by the cam angle modifying means; drive means for driving the cam angle modifying means; target value calculating means for calculating a target value depending on an operation state of the internal combustion engine; cam angle control means for controlling the cam angle detected by the cam angle detecting means to coincide with the target value calculated by the target value calculating means; learning means for learning a control signal outputted to the drive means at a time when the target value and the cam angle substantially coincide; and failure detecting means for detecting a failure of the cam angle modifying means, wherein the failure detecting means modifies a failure detection condition according to whether or not learning is completed by the learning means.