A method for monitoring and diagnosing an engine exhaust treatment of an internal combustion engine in a motor vehicle includes monitoring a nitrogen oxides (NOx) storage catalyst disposed in an engine exhaust stream downstream of the engine, determining a first diagnostic condition of the NOx storage catalyst based on data from a first EGT sensor and a second EGT sensor; determining a second diagnostic condition of the NOx storage catalyst based on a comparison of temperatures reported by a first NOx sensor and a second NOx sensor, selectively pausing the first diagnostic condition and the second diagnostic condition during a predetermined NOx storage catalyst regeneration period, and selectively generating a notification for an operator of the motor vehicle.