Home › Cummins Engines › 6766
Cummins Engines · 6766
Aftertreatment DEF Property Fault
What this code means
Aftertreatment 1 Diesel Exhaust Fluid Property - Data Valid But Below Normal Operating Range - Moderately Severe Level (DEF property fault; power derate per WholeFleet)
Applies to: all electronic engines.
Possible causes / checks (from the source)
SPN 3251, FMI 18
Need the part?
If diagnosis points to a failed sensor, solenoid, controller or harness part, send us the code (6766), machine model and serial number — we quote genuine and OEM replacement parts for export.
Ask for the replacement part on WhatsAppSource: 30-Minute DPF Clean — Cummins fault code list; cross-checked vs WholeFleet Cummins fault code list. Cross-checked in two independent sources. Compiled 2026-10-30. No manufacturer affiliation.