SPN 5967 FMI 15 — SCR ammonia slip high
What it means: SCR ammonia slip high.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Check dosing rate vs command
Don't risk it — look up listed providers near you and give them this SPN/FMI when you call.
Listed providers nearest Ocala, FL
Closest first. Tell them SPN 5967 FMI 15 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Ocala, FL · (352) 830-1899
- 0.0 mi away — based in Ocala, FL · (352) 620-0740
- 0.0 mi away — based in Ocala, FL · (352) 497-0277
Applies to: Sae
What SPN 5967 FMI 15 means
SCR ammonia slip high.
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
SCR ammonia slip high.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Overdosing DEF. Other possibilities include Aged SCR catalyst; Temperature sensor error.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside SPN 5967 FMI 15, or share the same subsystem.
- SCR Operator Inducement — Severe Derate Active (SPN 5246 FMI 0)
- Aftertreatment 1 Diesel Particulate Filter Differential Pressure - Data Valid But Above Normal Operating Range, Most Severe Level (DPF severely restricted / plugged) (SPN 3251 FMI 0)
- Aftertreatment 1 Diesel Exhaust Fluid Quality - Data Valid But Below Normal Operating Range, Most Severe Level (DEF quality/concentration incorrect) (SPN 4364 FMI 1)
- DPF Differential Pressure — Data Erratic (SPN 3251 FMI 2)
- DEF Dosing Unit — Not Responding Properly (SPN 3361 FMI 7)
- SCR Conversion Efficiency — Below Threshold (SPN 4364 FMI 18)
- DEF Quality — Out of Spec (SPN 4094 FMI 31)
- EGR Temperature — Too High (SPN 412 FMI 0)
Same symptom: DEF / SCR fault
Other codes in the DEF and SCR chain — the ones that end in an inducement countdown.
- Reductant System Performance Bank 1 (P204F) · Aftertreatment & Emissions
- Reductant Quality Deviation (P20EA) · Aftertreatment & Emissions
- DEF tank level low (SPN 1761 FMI 18) · Aftertreatment & Emissions
- DEF tank temp sensor — voltage high (SPN 3031 FMI 3) · Aftertreatment & Emissions
- Upstream NOx sensor — internal failure reported (SPN 3216 FMI 12) · Aftertreatment & Emissions
- SCR inlet NOx sensor — erratic (SPN 3216 FMI 2) · Aftertreatment & Emissions
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.