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SPN 3361 FMI 31 — DEF dosing unit — condition exists
SeriousAftertreatmentPower derate likely — plan to stop soon
Applies to: Sae
DEF dosing unit — condition exists.
Don't risk it — get a diesel tech on the truck.
Your SPN/FMI rides along, so nearby mechanics see the fault before they quote you.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Generic dosing fault flag
First moves (roadside)
- Check specific dosing codes alongside
FAQ
What does SPN 3361 FMI 31 mean?
DEF dosing unit — condition exists.
How serious is SPN 3361 FMI 31?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of SPN 3361 FMI 31?
The most common cause is: Generic dosing fault flag.
Can I keep driving with SPN 3361 FMI 31?
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Throwing this code right now?
Find a mechanic or related guides
General diagnostic guidance for heavy-duty diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack). Not a substitute for a scan-tool diagnosis on your specific truck.