Method and system for NOx sensor degradation
AssigneeFord Global Technologies, LLC
InventorsDevesh Upadhyay, In Kwang Yoo, Michiel J. Van Nieuwstadt, David John Kubinski
Life of this patent
Estimating the term…
Abstract
Various systems and method for detecting exhaust NOx sensor degradation are disclosed. In one example, degradation of the NOx sensor is indicated responsive to reductant injection in an exhaust passage under engine off conditions. For example, degradation of the NOx sensor is indicated when an actual NOx sensor output differs from an expected NOx sensor output by more than a threshold amount.
Claims20
A method for NOx sensor degradation detection in an engine exhaust having a reduction catalyst and a feedgas exhaust NOx sensor upstream of the reduction catalyst, comprising:
- shutting down an engine to rest;
- estimating an exhaust reductant level from the sensor following engine shutdown to rest;
- and
- indicating degradation of the feedgas exhaust NOx sensor by setting a flag based on the exhaust reductant level estimated by the sensor following engine shutdown to rest.
A method for an engine, comprising:
- following a vehicle-off condition, while an engine is at rest,
- injecting an amount of reductant into an exhaust passage;
- estimating an amount of reductant in the exhaust passage based on an output of a feedgas exhaust NOx sensor;
- and
- indicating NOx sensor degradation based on the injected amount relative to the estimated amount.
An engine system, comprising:
- an engine including an intake and an exhaust;
- a reductant injector configured to inject reductant into the engine exhaust, upstream of an exhaust reduction catalyst;
- a feedgas NOx sensor coupled to the engine exhaust downstream of the reductant injector and upstream of the reduction catalyst;
- and
- a controller configured with computer readable instructions for:
- during a first engine shutdown to rest, operating in a first mode to indicate reductant injector degradation based on an output of the NOx sensor;
- and
- during a second engine shutdown to rest, operating in a second mode to indicate NOx sensor degradation based on the output of the NOx sensor.
Dependencies are inferred from the claim text.