SPN 102 FMI 4 — Boost sensor — voltage low
What it means: Boost sensor — voltage low.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Unplug — invert
Don't risk it — look up listed providers near you and give them this SPN/FMI when you call.
Listed providers nearest Phoenix, AZ
Closest first. Tell them SPN 102 FMI 4 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 Phoenix, AZ · (623) 304-4187
- 0.0 mi away — based in Phoenix, AZ · (480) 458-7715
- 0.0 mi away — based in Phoenix, AZ · (480) 530-7347
Applies to: Detroit · Navistar · Paccar · Volvo
What SPN 102 FMI 4 means
Boost sensor — voltage low.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Short to ground
- Failed sensor
- Short ground
First moves (roadside)
- Unplug — invert
- Unplug and observe
FAQ
Boost sensor — voltage low.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Short to ground. Other possibilities include Failed sensor; Short ground.
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 102 FMI 4, or share the same subsystem.
- Boost pressure high (SPN 102 FMI 0)
- Boost Pressure Sensor — Voltage High (SPN 102 FMI 3)
- Engine Protection — Power Derate Active (SPN 1569 FMI 31)
- Intake Manifold (Charge Air) Temp — High (SPN 105 FMI 0)
- Turbo Boost Pressure — High / Overboost (SPN 1127 FMI 16)
- Intake manifold temp — voltage high (SPN 105 FMI 3)
- Intake manifold temp — voltage low (SPN 105 FMI 4)
- Injection control pressure low (HEUI — older engines) (SPN 164 FMI 1)
Same symptom: Charging and voltage
Other codes that trace back to voltage — one bad ground can set half a dozen of them at once.
- Turbo compressor inlet temp high voltage (SPN 1172 FMI 3) · Engine
- Turbo compressor inlet pressure — high voltage (SPN 1176 FMI 3) · Engine
- Exhaust back pressure sensor — high voltage (SPN 1209 FMI 3) · Engine
- Fuel shut-off valve — voltage high (SPN 3482 FMI 3) · Engine
- Sensor supply 1 (5V) — low voltage (SPN 3509 FMI 4) · Engine
- Sensor supply 2 — low voltage (SPN 3510 FMI 4) · Engine
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.