US Patent 7257941 Model based diagnostics of an aftertreatment fuel dosing system

The invention relates to systems and methods of detecting faults in an exhaust line fuel injection system. An expected relationship between a temperature within the exhaust system and a commanded fuel injection rate or amount is compared to an actual relationship in order to detect faults. The temperature is preferably a temperature of, within, or downstream of an exhaust system device that catalyzes an oxidation or partial oxidation reaction of the fuel, such as an oxidation catalyst or a fuel reformer. The expected relationship may be defined in terms of a thermal model of a system comprising the catalytic device. The invention can be used to detect spray quality faults or to detect fuel injector faults without the use of flow meter.