Diagnostic Overview
Cummins fault code 6255 is generally associated with emissions inducement or derate status. The ECM may restrict power because an aftertreatment-related condition has not been repaired or because the system has not completed the required confirmation procedure after repair. Causes commonly include unresolved DEF, SCR, NOx sensor, DPF, or regeneration faults. The repair path is to scan the full active and inactive code list, fix the root aftertreatment issue, verify system operation, and then perform the required reset or drive cycle.