Patent ID: 7418322

Claim:
An exhaust temperature sensor malfunction detecting apparatus for an engine having an exhaust cleaning device in an exhaust passage, comprising: an upstream temperature sensor disposed in the exhaust passage for detecting an upstream temperature of exhaust gas at an upstream position of the exhaust cleaning device; a downstream temperature sensor disposed downstream the upstream sensor in the exhaust passage for detecting a downstream temperature of the exhaust gas at a downstream position of the exhaust cleaning device; engine operation detecting means for detecting an operation condition of the engine; condition determining means for determining whether the engine is in a predetermined condition, the predetermined condition is a condition in which the exhaust cleaning device generates little catalytic reaction heat; estimating means for estimating one of a downstream temperature and an upstream temperature of the exhaust gas based on one of the detected upstream temperature and the detected downstream temperature, respectively, when the engine is in the predetermined condition; and malfunction determining means for determining a temperature sensor malfunction based on a relation between the one of the detected downstream temperature and the detected upstream temperature and the one of the estimated downstream temperature and the estimated upstream temperature.