Method and algorithm for performing an NH3 sensor rationality diagnostic

摘要

An example method includes interpreting an NH3 composition value at a position upstream of a selective reduction catalyst (SCR) element fluidly disposed in the exhaust conduit of an engine, interpreting a NOx composition value at a position downstream of the SCR element, and determining an NH3 sensor rationality threshold in response to the upstream NH3 composition value. The method further includes determining an NH3 sensor health value as indicating a sensor failure in response to the downstream NOx composition value exceeding the NH3 sensor rationality threshold.

主权项

1. A system, comprising:
an internal combustion engine producing an exhaust stream as a byproduct of operation; an exhaust conduit fluidly coupled to the engine, and structured to receive the exhaust stream; a selective reduction catalyst (SCR) element fluidly disposed in the exhaust conduit, the SCR catalyst having an upstream side and a downstream side; an NH3 sensor operationally coupled to the exhaust conduit and structured to provide an upstream side NH3 composition value; a NOx sensor operationally coupled to the exhaust conduit at a position downstream of the SCR element and structured to provide a downstream side NOx composition value; and a controller, comprising;
a composition module structured to interpret the upstream NH3 composition value and the downstream NOx composition value;an NH3 sensor threshold module structured to determine an NH3 sensor rationality threshold in response to the upstream NH3 composition value; andan NH3 sensor diagnostic module structured to determine an NH3 sensor health value for the NH3 sensor in response to a comparison of the downstream NOx composition value and the NH3 sensor rationality threshold.