Patent ID: 8756984

Claim:
An abnormality diagnosis apparatus for an internal combustion engine control system which is provided with a fuel pump discharging a high-pressure fuel, an accumulator accumulating the high-pressure fuel therein, and a fuel injector injecting the high-pressure fuel accumulated in the accumulator into the internal combustion engine, the abnormality diagnosis apparatus computing an actual torque generated by the internal combustion engine at a combustion cycle based on an instant speed of the internal combustion engine, the abnormality diagnosis apparatus performing a diagnosis of the internal combustion engine control system based on the computed actual torque, the abnormality diagnosis apparatus comprising: a torque determining portion computing the actual torque based on the instant speed of the internal combustion engine under a specified condition where the internal combustion engine is running, the fuel injector injects no fuel and the fuel pump discharges no fuel so that the fuel pressure in the accumulator is kept constant, the torque determining portion determining whether the actual torque is increased or decreased by the specified amount or more relative to a predetermined reference torque; a pressure variation detecting portion detecting a variation in fuel pressure in the accumulator under the specified condition; and an abnormality determining portion determining whether an abnormality occurs and identifying a type of the abnormality based on a determining result of the torque determining portion and the variation in fuel pressure in the accumulator detected by the pressure variation detecting portion.