There are only two serviceable items on the SCR system: the DEF filter and the DEF injector. The DEF filter is located at the base of the DEF module. The first cleaning should occur at six months and then annually. The DEF injector is located at the base of the DPF exhaust outlet. It should be inspected and cleaned annually.
Daimler Trucks North America has defined intervals for SCR system maintenance. It recommends checking/inspecting the system every 50,000 to 75,000 miles, which is consistent with most non-maintenance components, says Williamson. “The DEF filter needs to be changed every 250,000 miles for long-haul applications (150,000 miles for severe duty),” he adds. “The injector does not have a maintenance life — just check/inspect as needed.”
Other equipment, such as NOx sensors, are maintenance free and need no attention unless indicated by the onboard diagnostic system.
Keeping the current aftermarket emissions systems operating properly is not difficult. “Follow the factory recommended operation and maintenance procedures,” advises Moore. “If an emissions system problem occurs, have it fixed at an authorized repair facility immediately to avoid further complications. If the instrument cluster indicates DEF is low, fill the DEF tank right away.”
Simple steps can minimize downtime and prevent damage to expensive exhaust aftertreatment components.