Systems and methods for NO_xsensor diagnostics

摘要

Systems and methods are disclosed for diagnosing gain rationality of an NOx sensor that is downstream of a selective catalytic reduction (SCR) catalyst. Sensor diagnostics are performed while maintaining reductant dosing to the SCR catalyst.

主权项

1. A method, comprising:
setting a diagnostic dosing command for injection of reductant at an ammonia to oxides of nitrogen (NOx) ratio (ANR) rate that is less than a stoichiometric ANR rate; injecting reductant in response to the diagnostic dosing command; determining a reductant depletion time based on a temperature of a selective catalytic reduction (SCR) catalyst and a flow rate of an exhaust gas; depleting reductant deposits and reductant storage the SCR catalyst with the exhaust gas from an internal combustion engine for the determined reductant depletion time; determining an estimated system-out NOx amount based on a measured engine-out NOx amount upstream of the SCR catalyst and the ANR rate; determining a measured system-out NOx amount from a system-out NOx sensor downstream of the SCR catalyst; determining a gain error for the system-out NOx sensor based on a ratio of the measured system-out NOx amount to the estimated system-out NOx amount; determining a fault condition of the system-out NOx sensor based on the gain error; and providing the fault condition to a malfunction indicator means.