Diagnostic Overview
Cummins fault code 3146 is commonly tied to DEF quality, SCR performance, or emissions inducement logic. It may appear when the ECM determines that the DEF/SCR system is not meeting required emissions performance. Causes include contaminated DEF, incorrect DEF concentration, DEF dosing failure, faulty NOx sensors, exhaust leaks, or SCR catalyst degradation. This code should be diagnosed together with all other active aftertreatment codes because it may be a result code rather than the original failure.