Patent ID: 8813476

Claim:
A diagnosis apparatus for a reducing agent supply apparatus that diagnoses a reducing agent supply apparatus having a reducing agent addition valve that is provided in an exhaust system of an internal combustion engine and injects liquid reducing agent into exhaust gas, comprising: a temperature sensor that senses a temperature of the exhaust gas, provided at a position where spray of the reducing agent is formed as the reducing agent is injected through the reducing agent addition valve; and an electronic control unit including logic that, when executed, causes the electronic control unit to perform steps of: calculating a decrease in the temperature of the exhaust gas sensed by the temperature sensor as the reducing agent is injected through the reducing agent addition valve, estimating a quantity of reducing agent actually injected through the reducing agent addition valve based on the decrease in the temperature of the exhaust gas calculated by the electronic control unit, and diagnosing whether or not there is a malfunction in the reducing agent supply apparatus based on the quantity of reducing agent estimated by the electronic control unit, wherein the electronic control unit determines that there is a malfunction in the reducing agent supply apparatus if the difference between a quantity of reducing agent that should be injected through the reducing agent addition valve and the quantity of reducing agent estimated by the electronic control unit is larger than a threshold value where the reducing agent supply apparatus is normal.