Reagent doser diagnostic system and method

摘要

Systems and methods are disclosed for determining or diagnosing a reagent dosing system failure to provide sufficient reagent to an exhaust aftertreatment system that includes an SCR catalyst to satisfy a reagent dosing command. The method comprises injecting a quantity of a reagent with a dosing system over a dosing cycle in response to a dosing command to treat an exhaust gas in an exhaust system that includes a selective catalytic reduction catalyst, wherein the dosing system includes a pump operating via feedback control to maintain a generally stable pressure of the reagent downstream of the pump during the dosing cycle, wherein injecting the quantity of the reagent includes: suspending pressure feedback control of the pump during a diagnostic dosing period within the dosing cycle while maintaining a pump speed; injecting a portion of the quantity of the reagent while suspending pressure feedback control during the diagnostic dosing period; and determining a fault condition of the dosing system in satisfying the dosing command in response to a pressure drop of the dosing system during the diagnostic dosing period.