Patent ID: 8126637

Claim:
A control system for an internal combustion engine having a valve operating characteristic varying mechanism for continuously changing a lift amount of at least one intake valve of said engine, said valve operating characteristic varying mechanism including a control shaft for changing the lift amount, a motor for rotating said control shaft, and a transmission mechanism provided between an output shaft of said motor and said control shaft for transmitting an actuating force of said motor to said control shaft, said control system comprising: first rotational angle detecting means for detecting a rotational angle of the output shaft of said motor; second rotational angle detecting means for detecting a rotational angle of said control shaft; control means for performing a control of the lift amount of said at least one intake valve according to the rotational angle detected by said first rotational angle detecting means or said second rotational angle detecting means; and failure diagnosis means for performing a failure diagnosis of said first rotational angle detecting means, said second rotational angle detecting means, and said transmission mechanism based on the rotational angles detected by said first and second rotational angle detecting means.