Fluid quality sensing means with reference sensor

An oil quality diagnostic system of an internal combustion engine, comprising:

• an oil container containing an engine oil being used in said internal combustion engine;
• an oil filler passage fluidly connected to said oil container for said engine oil to flow therethrough during a refill process including an oil trap section holding a portion of said oil being refilled in said refill process as a reference oil;
• a first sensor generating a first sensing signal indicative of at least one property of said reference oil being held in said oil trap section;
• a second sensor generating a second sensing signal indicative of said at least one property of said engine oil in said oil container;
• and
• a diagnostic controller adapted to:
• determine a first aging factor value in response to said first sensing signal and said second sensing signal;
• and
• identify a first fault when said first aging factor value is higher than a predetermined threshold.

A method for detecting a quality of a fluid in a fluid system including a fluid container containing a system fluid being used in said fluid system, a fluid filler passage fluidly connected to said fluid container for said system fluid to flow therethrough during a refill process including a fluid trap section, a first sensing piece positioned in said fluid trap section, and a second sensing piece positioned in said fluid container, comprising:

• storing a portion of said system fluid in said fluid trap section as a reference fluid;
• determining a first impedance value of said first sensing piece;
• determining a second impedance value of said second sensing piece;
• calculating real parts of said first impedance value and said second impedance value;
• and
• determining an aging factor value in response to said real parts of said first impedance value and said second impedance value.