SPN 102 FMI 3 — Boost Pressure Sensor — Voltage High
What it means: The intake-manifold boost (MAP) pressure sensor signal is reading above its normal voltage range — usually a sensor, wiring, or short fault rather than true overboost.
How serious / can you keep driving: Caution. Limp to the next safe stop.
Check first: Inspect the boost-sensor connector and pigtail for corrosion, oil, or chafe.
Don't risk it — look up listed providers near you and give them this SPN/FMI when you call.
Listed providers nearest Indianapolis, IN
Closest first. Tell them SPN 102 FMI 3 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 Indianapolis, IN · (317) 789-5002
- 0.0 mi away — based in Indianapolis, IN · (317) 300-7000
- 0.0 mi away — based in Indianapolis, IN · (317) 646-8208
What SPN 102 FMI 3 means
The intake-manifold boost (MAP) pressure sensor signal is reading above its normal voltage range — usually a sensor, wiring, or short fault rather than true overboost. The ECM may limit fueling/boost, causing low power until it's resolved.
How serious is it?
Caution. Limp to the next safe stop.
Most likely causes
- Short-to-voltage or chafed wiring on the boost-sensor signal circuit
- Failed boost/MAP pressure sensor
- Connector corrosion or a backed-out pin at the sensor
- Soot/oil contamination fouling the sensor element
First moves (roadside)
- Inspect the boost-sensor connector and pigtail for corrosion, oil, or chafe.
- Compare commanded vs. actual boost in the data — a flat or pegged reading points to the sensor circuit.
- Check for a short-to-power on the signal wire before replacing the sensor.
- Clean or replace the sensor if the element is fouled with oil/soot.
Common misdiagnoses
- Chasing a turbo or wastegate problem when the sensor circuit is simply shorted high.
- Replacing the sensor without checking the harness for a short-to-voltage.
- Ignoring low-power complaints that are really this sensor limiting fuel.
FAQ
The intake-manifold boost (MAP) pressure sensor signal is reading above its normal voltage range — usually a sensor, wiring, or short fault rather than true overboost. The ECM may limit fueling/boost, causing low power until it's resolved.
Caution — Limp to the next safe stop.
The most common cause is: Short-to-voltage or chafed wiring on the boost-sensor signal circuit. Other possibilities include Failed boost/MAP pressure sensor; Connector corrosion or a backed-out pin at the sensor; Soot/oil contamination fouling the sensor element.
Limp to the next safe stop. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside SPN 102 FMI 3, or share the same subsystem.
- Boost pressure high (SPN 102 FMI 0)
- Boost sensor — voltage low (SPN 102 FMI 4)
- 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.