A failure diagnosis apparatus and method permit specification of a failed
atmospheric pressure sensor in an engine control apparatus having
redundant pressure detection systems to ensure failsafe control of the
engine. The apparatus includes a calculating unit that calculates a
difference between a first atmospheric pressure and a second atmospheric
pressure detected in respective pressure detection systems. A first
comparing unit outputs an alarm when the difference is larger than a
threshold value. A difference calculating unit calculates a first
difference between the first atmospheric pressure and a manifold
pressure. A difference calculating unit calculates a second difference
between the second atmospheric pressure and the manifold pressure. A
second comparing unit compares the first and second differences in
response to output of the alarm from the first comparing unit while an
engine is stopped. The sensor having abnormal function corresponds to the
one for which the difference is larger.