An exhaust gas treatment system for an internal combustion engine is provided having an exhaust gas conduit, a diesel exhaust fluid (“DEF”) source, a selective catalytic reduction (“SCR”) device, a NOx sensor, and a control module. The DEF source supplies a DEF having a quality factor. The NOx sensor is in fluid communication with the exhaust gas conduit. The NOx sensor is located downstream of the SCR device and is configured for detecting a NOx concentration value. The control module is in communication with the DEF source and the NOx sensor. The control module stores a diagnostic adaptation factor and an expected NOx value. The control module includes a dosing module for determining a controls adaptation factor that is based on a deviation between the NOx concentration value and the expected NOx value. The diagnostic adaptation factor is selectively updated with the controls adaptation factor.