Patent ID: 8303174

Claim:
A temperature sensor plausibility diagnosis unit which, in an exhaust purification apparatus of an internal combustion engine that delivers an additive inside a storage tank to an exhaust pipe on an upstream side of a reduction catalyst and selectively reduces and purifies NO x in exhaust with the reduction catalyst, is for performing plausibility diagnosis of a temperature sensor disposed inside the storage tank, the temperature sensor plausibility diagnosis unit comprising: an additive heat capacity calculating portion that calculates a heat capacity of the additive inside the storage tank; a heat quantity variation calculating portion that calculates an increase or decrease in a quantity of heat that the additive inside the storage tank receives; and a plausibility diagnosing portion that determines the plausibility of the temperature sensor by comparing an estimated temperature course of the additive estimated from the heat capacity of the additive and the increase or decrease in the quantity of heat with a sensor temperature course of the additive detected by the temperature sensor.