SPN 191 FMI 9 — Output shaft speed not updating (J1939)
What it means: Output shaft speed not updating (J1939).
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Check J1939
Don't risk it — look up listed providers near you and give them this SPN/FMI when you call.
Listed providers nearest Billings, MT
Closest first. Tell them SPN 191 FMI 9 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 Billings, MT · (406) 245-8985
- 0.0 mi away — based in Billings, MT · (406) 252-8413
- 0.0 mi away — based in Billings, MT · (406) 780-3711
Applies to: Eaton
What SPN 191 FMI 9 means
Output shaft speed not updating (J1939).
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Datalink
First moves (roadside)
- Check J1939
FAQ
Output shaft speed not updating (J1939).
Serious — Power derate likely — plan to stop soon.
The most common cause is: Datalink.
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 191 FMI 9, or share the same subsystem.
- Transmission output shaft speed erratic (SPN 191 FMI 2)
- Output shaft speed abnormal (SPN 191 FMI 8)
- Main shaft speed erratic (SPN 160 FMI 2)
- Input shaft speed erratic (SPN 161 FMI 2)
- Transmission output retarder speed erratic (SPN 162 FMI 2)
- Trans oil temperature very high (SPN 177 FMI 0)
- Trans oil temperature voltage high (SPN 177 FMI 3)
- Trans oil temperature voltage low (SPN 177 FMI 4)
Same symptom: Lost communication
Other datalink faults. A U-code is a network problem and is diagnosed at the datalink, not at the module that went quiet.
- Engine Oil Pressure — Extremely Low (SPN 100 FMI 1) · Lubrication
- High Speed CAN Bus Fault (U0001) · Electrical, Charging & Network
- Lost Communication with ECM/PCM (U0100) · Electrical, Charging & Network
- Lost Communication with Fuel Injector Control Module (U0105) · Electrical, Charging & Network
- Battery / Charging Voltage — Low (SPN 168 FMI 18) · Electrical, Charging & Network
- Lost J1939 datalink message from VECU (SPN 1807 FMI 9) · Brakes, ABS & Stability
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.