Diagnostic Overview
Cummins fault code 3142 generally relates to DEF dosing, DEF system pressure, or SCR performance. The ECM may be detecting that the DEF system cannot deliver the commanded amount of fluid or that the SCR system is not responding correctly. Common causes include a plugged DEF filter, failed DEF pump, crystallized DEF lines, blocked doser, contaminated DEF, wiring issues, or inaccurate NOx sensor feedback. The repair path should include checking DEF quality, pump pressure, doser operation, and any related SCR efficiency or inducement codes.
