Diagnostic Overview
Cummins fault code 3545 commonly points to an aftertreatment DEF/SCR system fault, often involving DEF dosing, system pressure, or aftertreatment performance monitoring. Causes may include poor DEF quality, a plugged DEF doser, DEF pump failure, crystallized DEF lines, faulty NOx sensors, exhaust leaks, or SCR efficiency problems. Diagnosis should begin by checking all active aftertreatment codes, testing DEF quality, verifying DEF pump pressure, and inspecting the doser and exhaust system.