Detection and identification of fuel injector failure modes

A process comprising:

• operating a fuel system to supply fuel to an internal combustion engine, the fuel system including a fuel rail configured to receive fuel from a fuel supply and to supply fuel to a plurality of fuel injectors, a pressure sensor operatively coupled with and configured to sense pressure of fuel in the fuel rail, an exhaust oxygen sensor, and an electronic control system operatively coupled with the engine, the plurality of fuel injectors, the pressure sensor, and the exhaust oxygen sensor;
• and
• operating the electronic control system to:
• receive a fuel pressure signal from the pressure sensor,
• process the pressure signal with a resonating filter,
• receive an exhaust oxygen signal from the exhaust oxygen sensor, and
• in response to an output of the resonating filter and the exhaust oxygen signal, diagnose one of an under-fueling failure mode and an over-fueling failure mode of an injector of the plurality of injectors.

An electronic controller apparatus comprising:

• a processor;
• and
• a non-transitory memory medium configured instructions executable by the processor to:
• receive a fuel pressure signal from a pressure sensor,
• process the pressure signal with a resonating filter,
• receive an exhaust oxygen signal from the exhaust oxygen sensor, and
• in response to an output of the resonating filter and the exhaust oxygen signal, diagnose one of an under-fueling failure mode and an over-fueling failure mode of an injector of a plurality of injectors.