Abstract: A method of assessing overall efficiency of a selective-catalytic-reduction catalyst includes monitoring instantaneous efficiency of the catalyst. The method also includes determining the overall efficiency by summing instantaneous efficiency values weighted by a first set of coefficients if the most recent instantaneous efficiency value is above an instantaneous efficiency threshold. The method additionally includes determining the overall efficiency by summing instantaneous efficiency values weighted by a second set of coefficients if the most recent instantaneous efficiency value is equal to or below the instantaneous efficiency threshold. Furthermore, the method includes determining whether the overall efficiency has dropped below an overall efficiency threshold and reporting when the overall efficiency has dropped below the overall efficiency threshold.

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 vehicle includes an engine, an exhaust system, a selective catalytic reduction (SCR) device, a first and a second NOx sensor configured to respectively measure an upstream and a downstream NOx level, and a controller or host machine. The controller, via the present method, calculates a NOx conversion efficiency rate of the SCR device using the NOx levels from the sensors. At the end of a key cycle when an accumulated amount of upstream NOx is less than a calibrated upstream NOx level, the controller determines if the NOx conversion efficiency rate is presently passing or failing. The accumulated upstream NOx is recorded in memory for use in calculating the NOx conversion efficiency rate during a subsequent key cycle only when the NOx conversion efficiency rate is presently passing at the end of the key cycle. A control system for the vehicle uses the controller and sensors as noted above.

Abstract: An exhaust diagnostic system includes an exhaust gas temperature management module that selectively increases a temperature of a selective catalytic reduction (SCR) catalyst to a predetermined testing temperature range using an intrusive exhaust gas temperature management approach. An SCR efficiency testing module estimates an efficiency of the SCR catalyst while the temperature is within the predetermined temperature range.

Abstract: A control system for a selective catalytic reduction (SCR) system includes a dosing control module, a comparison module, and a status determination module. The dosing control module controls a dosing system to inject a desired amount of ammonia into exhaust gas at a first location in an exhaust stream. The comparison module compares a measured amount of ammonia in the exhaust gas to the desired amount of ammonia, wherein the measured amount of ammonia is measured at a second location downstream from the first location and upstream from or within an SCR catalyst. The status determination module determines a pass/fail status of a component of the dosing system based on the comparison between the measured amount of ammonia and the desired amount of ammonia.

Abstract: A control system for a selective catalytic reduction (SCR) system includes a conversion efficiency determination module, an ammonia slip determination module, and a diagnostic module. The conversion efficiency determination module determines a conversion efficiency of an SCR catalyst. The ammonia slip determination module determines an amount of ammonia slip across the SCR catalyst when the conversion efficiency is less than a predetermined threshold. The diagnostic module determines pass/fail statuses of a reductant supply and the SCR catalyst based on the amount of ammonia slip and at least one ammonia slip threshold.

Abstract: A reductant injector is configured to dispense a reductant into an exhaust gas feedstream of an internal combustion engine upstream of a selective catalytic reduction device. The reductant injector of a reductant injection system is monitored by generating injector pulsewidth commands corresponding to a prescribed reductant flowrate, monitoring the injector pulsewidth commands, verifying the prescribed reductant flowrate corresponds to the injector pulsewidth commands, monitoring a fluidic pressure in the reductant injection system, estimating a first injected quantity of the reductant corresponding to the injector pulsewidth commands, estimating a second injected quantity of the reductant corresponding to the fluidic pressure in the reductant injection system, and comparing the first and second injected quantities of reductant.

Abstract: A diagnostic control module includes a temperature gradient module. The temperature gradient module determines a temperature gradient across a selective catalytic reduction (SCR) catalyst of an exhaust system of an engine based on a plurality of temperature signals. A calibration module determines a weighted average based on the plurality of temperature signals. A SCR efficiency control module disables conversion efficiency monitoring based on the temperature gradient and the weighted average.

Abstract: An internal combustion engine operating at a lean air/fuel ratio includes a reductant injection system configured to dispense reductant into an exhaust gas feedstream upstream of a selective catalytic reduction device. The reductant injection system includes a reductant delivery system fluidly coupled to a reductant dispensing device that is configured to dispense the reductant. A method for monitoring the reductant injection system includes commanding the reductant dispensing device to dispense reductant at a prescribed reductant flowrate, controlling the reductant delivery system to a preferred operating state, monitoring operation of the reductant delivery system and estimating a reductant flowrate as a function of the monitored operation of the reductant delivery system, and diagnosing operation of the reductant injection system as a function of the prescribed reductant flowrate and the estimated reductant flowrate.

Abstract: An exhaust diagnostic system includes an exhaust gas temperature management module that selectively increases a temperature of a selective catalytic reduction (SCR) catalyst to a predetermined testing temperature range using an intrusive exhaust gas temperature management approach. An SCR efficiency testing module estimates an efficiency of the SCR catalyst while the temperature is within the predetermined temperature range.

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 selective catalytic reduction (SCR) system includes a first sensor that determines a first concentration of NOx, a second sensor that determines a second concentration of NOx and NH3, and a fault determination module. The fault determination module diagnoses a fault in at least one of a dosing agent and a catalyst in an SCR device based on the first and second concentrations.