Systems and methods for diagnosing NOx sensor based on ammonia slip

A method for diagnosing a sensor, comprising:

• receiving data indicative of operating conditions of at least one of an engine or of an aftertreatment system;
• determining, during a first period of time, that an amount of NOx output from the aftertreatment system satisfies a low NOx operating mode condition based on the data indicative of operating conditions;
• determining, during a second period of time, that operating conditions for a first conversion efficiency are present based on the data indicative of the operating conditions of the aftertreatment system;
• responsive to the determination that operating conditions for the first conversion efficiency are present, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition;
• retrieving a minimum value of the amount of NOx output from the aftertreatment system during the first period of time;
• retrieving a maximum value of the amount of NOx output from the aftertreatment system during the second period of time;
• and
• selectively setting an alert based on the retrieved minimum value and the retrieved maximum value of the amount of NOx outputs.

A non-transitory computer-readable medium storing instructions therein that, when executed by at least one processor of a controller, cause the controller to perform operations comprising:

• receiving data indicative of an operating condition of at least one of an engine or an aftertreatment system;
• determining, during a first period of time, that an amount of NOx output from the aftertreatment system satisfies a low NOx operating mode condition based on the data indicative of the operating conditions;
• determining, during a second period of time, that operating conditions for a first conversion efficiency are present based on the data indicative of the operating conditions of the aftertreatment system;
• responsive to the determination that operating conditions for the first conversion efficiency are present, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition;
• retrieving a minimum value of the amount of NOx output from the aftertreatment system during the first period of time;
• retrieving a maximum value of the amount of NOx output from the aftertreatment system during the second period of time;
• and
• selectively setting an alert based on the retrieved minimum value and the retrieved maximum value of the amount of NOx outputs.