In 2013 SCR became standard on Cummins engines in school buses. The SCR system along with a diesel particulate filter (DPF) is used to meet emissions standards. The DPF collects soot (particulate) and has to be cleaned out when the soot reaches a certain level. This video describes the process and what a driver will see when regeneration is occurring. Also how a technician can do a forced regeneration if normal driving conditions don’t allow a passive regeneration to occur.
/ / Blue Bird School Bus Regeneration