Abnormality diagnosing apparatus

An abnormality diagnosing apparatus configured to diagnose abnormality of a fuel injection amount of a fuel injection device configured to inject a fuel into each cylinder of a diesel engine, the abnormality diagnosing apparatus comprising:

• an oxidation catalyst provided in an exhaust gas passage;
• a first exhaust gas temperature sensor configured to detect an upstream-side exhaust gas temperature, the upstream-side exhaust gas temperature being an exhaust gas temperature on an upstream side of the oxidation catalyst;
• a second exhaust gas temperature sensor configured to detect a downstream-side exhaust gas temperature, the downstream-side exhaust gas temperature being an exhaust gas temperature on a downstream side of the oxidation catalyst;
• and
• a controller detecting a condition of the diesel engine;
• wherein the controller is:
• configured to retrieve the upstream-side exhaust gas temperature detected by the first exhaust gas temperature sensor and the downstream-side exhaust gas temperature detected by the second exhaust gas temperature sensor when a predetermined condition that the diesel engine is operated and a post-injection is not being carried out;
• configured to determine whether a difference between the upstream-side exhaust gas temperature and the downstream-side exhaust gas temperature is higher or not higher than an excessive determination value;
• and
• configured to determine the fuel injection amount, which is used for operating the diesel engine, of the fuel injection device, at the predetermined condition that the diesel engine is operated, is excessive in case the difference between the upstream-side exhaust gas temperature and the downstream-side exhaust gas temperature is higher than the excessive determination value.