SPN 157 FMI 0Fuel
Fuel Rail Pressure Sensor Circuit Low
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 157 / FMI 0
Category
Fuel
Derate Risk
Possible
Regen Inhibit
No
Inducement Risk
No
Component Location: Fuel rail pressure sensor is mounted on the high-pressure fuel rail, typically on the driver side of the engine near the fuel injectors.
Common Symptoms
- Engine fails to start or hard starting
- Engine cranks but does not run
- Loss of power and engine derate
- Rough idle and misfiring
- Check engine light illuminated
- Engine stalling under load
Root Causes
- Faulty fuel rail pressure sensor Damaged or corroded wiring harness to fuel rail pressure sensor Poor electrical connection at sensor connector Shorted sensor circuit to ground Water intrusion in sensor connector
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Derate Behavior
Power Derate
Possible
System Interactions
SPN 157 FMI 0 interacts with the following systems and may trigger cascading faults if not resolved promptly.
Common Diagnostic Mistakes
Replacing the sensor without verifying wiring continuity and supply voltage first.
Clearing codes without identifying and resolving the root cause — the fault will return.
Ignoring related active faults — cascading faults often share a root cause.
Skipping the connector inspection — corrosion and damaged pins are a leading cause of sensor faults.
Condemning the ECM before exhausting all wiring and component tests.
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OEM System Resources
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 157 FMI 0 — Full FSM Sequence & Repair Steps — includes wiring notes, sensor specs, and gated repair procedures.
Authority References
Diagnostic procedures on this page are informed by OEM service literature and industry standards.
Cummins QuickServe OnlineOfficial Cummins service manuals, fault code lookup, and TSB database.Detroit Diesel DiagnoCentralDetroit Diesel diagnostic procedures, DDDL documentation, and service literature.PACCAR MX Engine ServicePACCAR MX-11 and MX-13 engine service documentation and DAVIE diagnostic guides.Volvo/Mack Tech ToolVolvo and Mack engine fault code reference and PTT/Tech Tool diagnostic procedures.ASE — Diesel Truck Technician CertificationNational Institute for Automotive Service Excellence — T2 Diesel Engines certification standards.EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx standards.
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