Systems and methods for aftertreatment system diagnostics

An apparatus, comprising:

• an exhaust aftertreatment system including an oxidation catalyst and an SCR catalyst downstream of the oxidation catalyst;
• a first NOx sensor upstream of the oxidation catalyst;
• a second NOx sensor downstream of the oxidation catalyst and upstream of the SCR catalyst;
• a programmable controller in communication with the first and second NOx sensors, the controller including:
• an NOx amount detection module configured to determine a first NOx amount from the first NOx sensor and a second NOx amount from the second NOx sensor;
• an oxidation catalyst health determination module configured to determine a health indicator value of the oxidation catalyst based at least in part on a difference between the first and second NOx amounts, wherein the oxidation catalyst health determination module is configured to determine the health indicator value as a ratio comprising the difference between first NOx amount and the second NOx amount divided by the first NOx amount;
• and
• an oxidation catalyst health reporting module configured to provide an indication of oxidation catalyst health degradation when the health indicator value is less than a threshold ratio, wherein the threshold ratio is based on a sensitivity of the first and second NOx sensors to NO2 in the NOx amount, wherein the threshold ratio is 15%, wherein each of the NOx amount detection module, the oxidation catalyst health determination module, and the oxidation catalyst health reporting module is implemented in at least one of hardware and a non-transitory computer readable medium.

A system, comprising:

• an internal combustion engine structured to provide an exhaust stream containing NOx to an aftertreatment system;
• an oxidation catalyst in the aftertreatment system that is structured to oxidize an amount of NOx in the exhaust stream;
• an SCR catalyst downstream of the oxidation catalyst structured to receive the oxidized exhaust stream from the oxidation catalyst;
• a first sensor operatively coupled to the exhaust stream at a first position upstream of the oxidation catalyst, the first sensor structured to detect an NOx amount in the exhaust stream at the first position;
• a second sensor operatively coupled to the exhaust stream at a second position downstream of the oxidation catalyst and upstream of the SCR catalyst, the second sensor structured to detect an NOx amount in the exhaust stream at the second position;
• and
• a controller in communication with the first and second sensors, the controller configured to determine a health indicator value of the oxidation catalyst as a ratio comprising the difference between the NOx amount at the first position and the NOx amount at the second position divided by the NOx amount at the first position, wherein the controller is configured to output an indication of oxidation catalyst health degradation when the health indicator value is less than a threshold ratio, wherein the threshold ratio is based on a sensitivity of the first and second sensors to NO2 in the NOx amount, wherein the threshold ratio is 15%.