A system may include a NOx sensor and a controller. The controller may be configured to interpret a value of a first parameter indicative of an amount of NOx measured by the NOx sensor and interpret a value of a second parameter for a NOx value from a look-up table. The controller may be further configured to determine a correction factor based on the value of the first parameter and the value of the second parameter and generate a dosing command based, at least in part, on the determined correction factor. In some implementations, the NOx value from the look-up table may be based on one or more operating conditions of an engine. In some implementations, the controller may be further configured to update a NOx value of the look-up table based on the determined correction factor.