Patent ID: 8060291

Claim:
A control system for an internal combustion engine, the system comprising: an actuator that operates in a predetermined operating range to change a state quantity of an internal combustion engine; history detecting means, wherein, under a power supplying state, the history detecting means detects change history of the state quantity from an initial value at the start of the power supplying; a volatile memory for storing the change history detected by the history detecting means; and a backup power source for supplying power to the history detecting means and the volatile memory, the control system computing an actual value of the state quantity based on the change history stored in the volatile memory and the initial value, the control system further comprising: remaining data determining means, wherein after power supply by the backup power source is restored from a state in which the power supply is temporarily suspended, the remaining data determining means determines whether or not remaining data of the change history remaining in the volatile memory are the data that have been stored immediately before the suspension of power supply; initial value setting means, wherein, when the remaining data determining means determines that the remaining data of the change history are the data that have been stored immediately before the suspension of power supply, the initial value setting means sets the initial value to an actual value of the state quantity that is computed based on the remaining data; and reference value learning means, wherein, when the remaining data determining means determines that the remaining data is not the data that have been stored immediately before the suspension of power supply, the reference value learning means moves the actuator to a limit position in the operating range, sets the initial value to a reference value of the state quantity that corresponds to the limit position, and clears the change history, wherein, in a case where temporary suspension of the power supply from the backup power source reoccurs before completion of the reference value learning by the reference value learning means, the control system invalidates determination of the remaining data determining means and causes the reference value learning means to carry out the reference value learning, after restoration of the power supply.