System and method for diagnosing egr performance using nox sensor

A method for diagnosing a condition of an EGR valve used in an engine system, such EGR valve controlling a portion of exhaust gases fed back to an intake of such engine system, such engine system including an NOx sensor for measuring NOx in such exhaust, such method comprising:

• determining a time rate of change in NOx measured by the NOx sensor;
• comparing the determined time rate of change in the measured NOx with a predetermined expected time rate of change in measured NOx;
• and
• determining from the NOx measured by the NOx sensor and engine operating conditions indications of instances when samples of such measured NOx are greater than an expected maximum NOx level for such engine condition and less than an expected minimum NOx level for such engine condition.

A system for diagnosis a condition of an EGR valve used in an engine system, such engine system comprising:

• a NOx sensor for measuring NOx in exhaust gases from such engine system;
• an EGR valve for controlling a portion of the exhaust gases fed back to an intake of such engine system;
• and
• a controller for:
• determining a time rate of change in NOx measured by the NOx sensor;
• comparing the determined time rate of change in the measured NOx with a predetermined expected time rate of change in measured NOx;
• and
• determining the condition of the EGR valve as a function of such comparison.

A system for diagnosing a condition of an EGR valve used in an engine system, such engine system comprising:

• a NOx sensor for measuring NOx in exhaust gases from such engine system;
• an EGR valve for controlling a portion the exhaust gases produced by such engine system and fed back to an intake of such engine system;
• and
• a controller for:
• determining from NOx measured by the NOx sensor and engine operating conditions indications of instances when samples of such measured NOx are greater than an expected maximum NOx level for such engine condition and less than an expected minimum NOx level for such engine condition;
• and
• determining the condition of the EGR valve as a function of a statistical analysis of such indications.

A system for diagnosing a condition of an EGR valve used in an engine system, such engine system comprising:

• a NOx sensor for measuring NOx in exhaust gases from such engine system;
• an EGR valve for controlling a portion the exhaust gases produced by such engine system and fed back to an intake of such engine system;
• and
• a controller for:
• determining a time rate of change in NOx measured by the NOx sensor;
• comparing the determined time rate of change in the measured NOx with a predetermined expected time rate of change in measured NOx;
• and
• determining from the NOx measured by the NOx sensor and engine operating conditions indications of instances when samples of such measured NOx are greater than an expected maximum NOx level for such engine condition and less than an expected minimum NOx level for such engine condition.

An article of manufacture, comprising:

• a computer storage medium having a computer program encoded therein for method for diagnosing a condition of an EGR valve used in an engine system, such EGR valve controlling a portion of exhaust gases fed back to an intake of such engine system, such engine system including an NOx sensor for measuring NOx in such exhaust, such computer storage medium comprising:
• code for determining a time rate of change in NOx measured by the NOx sensor;
• code for comparing the determined time rate of change in the measured NOx with a predetermined expected time rate of change in measured NOx;
• and
• code determining the condition of the EGR valve as a function of such comparison.

An article of manufacture, comprising:

• a computer storage medium having a computer program encoded therein for diagnosing a condition of an EGR valve used in an engine system, such EGR valve controlling a portion exhaust gases produced by such engine system and fed back to an intake of such engine system, such engine system including an NOx sensor for measuring NOx in such exhaust, such computer storage medium comprising:
• code for determining from NOx measured by the NOx sensor and engine operating conditions indications of instances when samples of such measured NOx are greater than an expected maximum NOx level for such engine condition and less than an expected minimum NOx level for such engine condition;
• and
• code for determining the condition of the EGR valve as a function of a statistical analysis of such indications.

An article of manufacture, comprising:

• a computer storage medium having a computer program encoded therein for diagnosing a condition of an EGR valve used in an engine system, such EGR valve controlling a portion of exhaust gases fed back to an intake of such engine system, such engine system including an NOx sensor for measuring NOx in such exhaust, such computer storage medium comprising:
• code for determining a time rate of change in NOx measured by the NOx sensor;
• code for comparing the determined time rate of change in the measured NOx with a predetermined expected time rate of change in measured NOx;
• and
• code for determining from the NOx measured by the NOx sensor and engine operating conditions indications of instances when samples of such measured NOx are greater than an expected maximum NOx level for such engine condition and less than an expected minimum NOx level for such engine condition.