Patent ID: 7203594

Claim:
A failure diagnostic apparatus for atmospheric pressure sensors used in an engine control system having a first atmospheric pressure sensor that performs main control, a second atmospheric pressure sensor that backs up the first atmospheric pressure sensor, a manifold pressure sensor, an engine revolution detector, and a throttle sensor, said failure diagnostic apparatus comprising: an abnormality recognizing unit that outputs an abnormal signal when a difference between a first detected atmospheric pressure value detected by the first atmospheric pressure sensor and a second detected atmospheric pressure value detected by the second atmospheric pressure sensor exceeds a threshold value; an atmospheric pressure estimating unit that outputs an estimated atmospheric pressure value in response to input of engine revolution, a throttle opening, and a manifold pressure value according to a predetermined mutual relation among the engine revolution, the throttle opening, and the manifold pressure, and the atmospheric pressure; and an abnormality identifying unit that calculates differences between the first detected atmospheric pressure value and the second detected atmospheric pressure value with respect to the estimated atmospheric pressure value, respectively, and identifies as a failed sensor the atmospheric pressure sensor that detected the atmospheric pressure value having a larger calculated difference, wherein identification of the failed sensor by the abnormality identifying unit is performed in response to an output of the abnormal signal.