In modern diesel exhaust aftertreatment systems (EATS), the combination of a catalytic coating for selective catalytic reduction (SCR) and a diesel particulate filter (DPF) enables the simultaneous particulate filtration and reduction of nitrogen oxides. Particularly at low exhaust temperatures, the soot regeneration of a particulate filter is primarily influenced by the NO2 supply in the exhaust gas and thus by the activity of the diesel oxidation catalyst (DOC) upstream of the SCR-coated DPF (SDPF). Several investigations found that in filters with SCR coating and dosing of the urea-water solution (UWS) upstream of the filter, particle oxidation is partially inhibited by the presence of NH3. As the filter load increases, the flow resistance grows, which unavoidably leads to an increase in the exhaust gas back pressure. This enlarges the internal work of the engine and thus compromises brake thermal efficiency. The present investigation on the engine test bench is intended to clarify how the particle loading of the filter develops during a cycle with low engine power when operating with either a new or an aged DOC as a function of the operating time. These low-load cycle experiments were carried out on a modern six-cylinder railway engine with the latest stage V exhaust gas aftertreatment system. The loading of the SDPF was determined by means of repeated conditioned gravimetric measurements on the one hand and predicted by pre-validated numerical simulations on the other. The results show a clear influence of both the engine load in the cycle and the activity of the DOC on the particle loading. In addition, the UWS dosing has a significant influence on the filter loading, consisting of soot and urea reaction products. However, at the studied conditions, critical loads are only likely if the DOC has little or no remaining activity for hydrocarbon oxidation, as HC presence plays a significant role in soot oxidation behaviour.