Abstract: A method and control system for a selective catalytic reduction (SCR) catalytic converter and an ammonia dosing module that stores ammonia in a selective catalyst reducing (SCR) catalyst and that depletes the ammonia level by discontinuing or reducing dosing. The control system also includes an SCR conversion efficiency module that determines an SCR efficiency. An SCR efficiency comparison module compares the SCR efficiency to an efficiency threshold and generates a fault indicator when the SCR efficiency is not above the efficiency threshold.

Abstract: A method and system for determining conversion of NO to NO2 in an engine exhaust stream by an oxidation catalyst during operation of the engine is disclosed based on injecting hydrocarbon fuel into the exhaust stream upstream of the oxidation catalyst, measuring a temperature of the exhaust stream on the upstream and downstream sides of the oxidation catalyst, calculating a difference in exhaust stream temperature between the upstream and downstream sides of the oxidation catalyst, and determining the conversion of NO to NO2 by the oxidation catalyst from the difference in exhaust stream temperature based on a predetermined correlation profile between the temperatures on the upstream and downstream sides of the oxidation catalyst and conversion of NO to NO2.

Abstract: An exhaust diagnostic system includes a selective catalyst reduction (SCR) efficiency testing module that determines an efficiency of a SCR catalyst. An exhaust gas temperature management module selectively adjusts a temperature of the SCR catalyst to a predetermined temperature range using intrusive exhaust gas temperature management. A test enabling module initiates an SCR efficiency test using the SCR efficiency module after failing a prior SCR efficiency test and while the temperature of the SCR catalyst is within the predetermined temperature range.

Abstract: A method and system for determining conversion of NO to NO2 in an engine exhaust stream by an oxidation catalyst during operation of the engine is disclosed based on injecting hydrocarbon fuel into the exhaust stream upstream of the oxidation catalyst, measuring a temperature of the exhaust stream on the upstream and downstream sides of the oxidation catalyst, calculating a difference in exhaust stream temperature between the upstream and downstream sides of the oxidation catalyst, and determining the conversion of NO to NO2 by the oxidation catalyst from the difference in exhaust stream temperature based on a predetermined correlation profile between the temperatures on the upstream and downstream sides of the oxidation catalyst and conversion of NO to NO2.

Abstract: A sensor diagnostic system comprises first, second, and third dosing agent sensors and a control module. The first, second, and third dosing agent sensors indicate whether a dosing agent is present at first, second, and third volumetric levels of a dosing agent tank, respectively. The second volumetric level is greater than the first volumetric level and the third volumetric level is greater than the second volumetric level. The control module selectively diagnoses a sensor fault in at least one of the first, second, and third dosing agent sensors based on the indications of the first, second, and third dosing agent sensors.

Abstract: An exhaust diagnostic system includes a selective catalyst reduction (SCR) efficiency testing module that determines an efficiency of a SCR catalyst. An exhaust gas temperature management module selectively adjusts a temperature of the SCR catalyst to a predetermined temperature range using intrusive exhaust gas temperature management. A test enabling module initiates an SCR efficiency test using the SCR efficiency module after failing a prior SCR efficiency test and while the temperature of the SCR catalyst is within the predetermined temperature range.

Abstract: A method and control system for a selective catalytic reduction (SCR) catalytic converter and an ammonia dosing module that stores ammonia in a selective catalyst reducing (SCR) catalyst and that depletes the ammonia level by discontinuing or reducing dosing. The control system also includes an SCR conversion efficiency module that determines an SCR efficiency. An SCR efficiency comparison module compares the SCR efficiency to an efficiency threshold and generates a fault indicator when the SCR efficiency is not above the efficiency threshold.

Abstract: A sensor diagnostic system comprises first, second, and third dosing agent sensors and a control module. The first, second, and third dosing agent sensors indicate whether a dosing agent is present at first, second, and third volumetric levels of a dosing agent tank, respectively. The second volumetric level is greater than the first volumetric level and the third volumetric level is greater than the second volumetric level. The control module selectively diagnoses a sensor fault in at least one of the first, second, and third dosing agent sensors based on the indications of the first, second, and third dosing agent sensors.