Abnormality detection apparatus and method for oil level sensor

An abnormality detection apparatus for detecting an abnormality of an oil level sensor having a lower oil level detector adapted to produce an output that changes as an oil level in an oil pan of an internal combustion engine changes across a first reference oil level and an upper oil level detector adapted to produce an output that changes as the oil level in the oil pan changes across a second reference oil level that is higher than the first reference oil level, the first reference oil level and the second reference oil level being set such that the oil level falls between the first reference oil level and the second reference oil level when the internal combustion engine is operating and the oil level is higher than the second reference oil level when the internal combustion engine is not operating, the abnormality detection apparatus comprising:

• a pre-engine-start upper-oil-level-detector output recording portion that records an output of the upper oil level detector before the internal combustion engine is started;
• and
• an abnormality determining portion that determines that the upper oil level detector has an abnormality if the output of the lower oil level detector is indicating, after the start of the internal combustion engine, that the oil level is higher than the first reference oil level while the output of the upper oil level detector recorded by the pre-engine-start upper-oil-level-detector output recording portion is indicating that the oil level was lower than the second reference oil level before the start of the internal combustion engine.