DTC Hub Commercial Truck & Diesel Fault Codes
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Def Warning — Possible Fault Codes

Found 7 fault codes associated with def warning. Codes are sorted by severity — check STOP ENGINE codes first.

⚠️ 1 STOP ENGINE-level code associated with this symptom. Do not continue driving.
SPN 4364 FMI 18
SCR Inducement
Volvo D13 • Component: SCR Aftertreatment System • J1939
🔴 STOP ENGINE
SPN 4364 FMI 18
SCR Inducement Active
Cummins X15 • Component: Selective Catalytic Reduction (SCR) System • J1939
🟡 CHECK AT NEXT STOP
SPN 4334 FMI 7
DEF Dosing Valve Mechanical Fault
Cummins X15 • Component: DEF Dosing Valve (DMU) • J1939
🟡 CHECK AT NEXT STOP
SPN 1761 FMI 18
DEF Tank Level critically low
Detroit Diesel DD15 • Component: DEF Tank / DEF Level Sensor • J1939
🟡 CHECK AT NEXT STOP
SPN 4375 FMI 7
DEF Pump Module Failure
Volvo D13 • Component: DEF Pump Assembly • J1939
🟡 CHECK AT NEXT STOP
SPN 3031 FMI 9
DEF Quality Abnormal
Cummins X15 • Component: DEF Quality Sensor / DEF Tank • J1939
🟠 CHECK SOON
SPN 3031 FMI 9
DEF Quality Sensor
Volvo D13 • Component: DEF Concentration Sensor • J1939
🟠 CHECK SOON
⚠️ Diagnostic Note: Symptoms can have multiple root causes. Always verify with a diagnostic scan tool before replacing parts. The fault codes listed above are possible matches for def warning based on SAE J1939/J1587 fault code definitions and OEM service documentation.