Method and algorithm for diagnosing an NH3 sensor in an SCR system using measurements from two channels of the sensor

摘要

A system includes an internal combustion engine providing exhaust gases to an exhaust conduit, an aftertreatment system having an SCR catalyst component and disposed in the exhaust conduit. The system further includes a first NH3 sensing element preferentially sensitive to NH3 and a second NH3 sensing element preferentially sensitive to NO2 in the exhaust conduit. Both NH3 sensing elements are positioned downstream of the SCR catalyst component. The system includes a controller having a test conditions module that determines whether an NO2 concentration downstream of the SCR catalyst component is below a threshold value, an NH3 diagnostic module that provides a detection comparison value in response to the NO2 concentration, a first signal from the first NH3 sensing element, and a second signal from the second NH3 sensing element. The controller includes a sensor condition module that provides an NH3 sensor condition value in response to the detection comparison value.

主权项

1. A system, comprising:
an internal combustion engine providing exhaust gases to an exhaust conduit; an aftertreatment system disposed in the exhaust conduit, the aftertreatment system comprising a selective catalytic reduction (SCR) catalyst component; a first NH3 sensing channel operationally coupled to the exhaust conduit at a position downstream of the SCR catalyst component, the first NH3 sensing channel sensitive to NH3; a second NH3 sensing channel operationally coupled to the exhaust conduit at the position downstream of the SCR catalyst component, the second NH3 sensing channel more sensitive to NO2 than the first NH3 sensing channel, and the first NH3 sensing channel is more sensitive to NH3 than the second NH3 sensing channel; and a electronic controller operationally coupled to and configured to interpret a first signal from the first NH3 sensing channel and a second signal from the second NH3 sensing channel, wherein the first and second NH3 sensing channels are operationally coupled at a position downstream of the SCR catalyst component, the controller being configured to determine whether an NO2 concentration at the position downstream of the SCR catalyst component is below a threshold value, the controller being configured to not enable an NH3 sensor condition diagnostic in response to the NO2 concentration being above the threshold value and to enable the NH3 sensor condition diagnostic to provide a detection comparison value in response to the NO2 concentration being below the threshold value, and further in response to a first signal from the first NH3 sensing channel and a second signal from the second NH3 sensing channel, the controller further being configured to provide an NH3 sensor condition value in response to the detection comparison value.