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SPN 5967 FMI 15 — SCR ammonia slip high
SeriousAftertreatmentPower derate likely — plan to stop soon
Applies to: Sae
SCR ammonia slip high.
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
- Overdosing DEF
- Aged SCR catalyst
- Temperature sensor error
First moves (roadside)
- Check dosing rate vs command
- SCR temps
FAQ
What does SPN 5967 FMI 15 mean?
SCR ammonia slip high.
How serious is SPN 5967 FMI 15?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of SPN 5967 FMI 15?
The most common cause is: Overdosing DEF. Other possibilities include Aged SCR catalyst; Temperature sensor error.
Can I keep driving with SPN 5967 FMI 15?
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.