A lean NOX trap is a diesel exhaust aftertreatment system is selectively denitrated in a manner that addresses unreliability of NOX sensor data. According to one concept, data from a NOX is ignored or given decreased weight in a period immediately following a denitration. According to another concept, denitration is made contingent on both a first and a second criteria being met. The first criteria relates to the amount of NOX stored in the LNT or remaining NOX storage capacity of the LNT. The second criteria relates to the current performance of the exhaust treatment system, or a portion thereof, as determined from one or more measurements of NOX concentration in the exhaust. This reduces premature denitrations and associated unnecessary fuel expenditures resulting from inaccurate NOX concentration data and transient events