SPN 175 FMI 2Engine Protection
Engine Oil Temperature - Data Erratic, Intermittent or Incorrect
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Overview
Fault Code
SPN 175 / FMI 2
Category
Engine Protection
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The engine oil temperature sensor is typically threaded into the engine block, oil gallery, or oil filter housing, depending on OEM and engine family.
Common Symptoms
- Intermittent or erratic engine oil temperature gauge readings
- MIL or amber warning lamp illuminated
- Engine derate or power reduction in some configurations
- Fault code active or inactive with no clear pattern
- Oil temperature reading spikes or drops to implausible values
- Engine protection mode activation
Root Causes
- Faulty or contaminated engine oil temperature (EOT) sensor
- Loose, corroded, or damaged connector at the EOT sensor
- Chafed or intermittent wiring harness between sensor and ECM
- Water or oil intrusion into the sensor connector
- Out-of-range sensor resistance causing erratic signal
- Poor ECM ground or supply voltage irregularity
- Failed or degraded ECM sensor input circuit
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Derate Behavior
Power Derate
No
System Interactions
SPN 175 FMI 2 interacts with the following systems and may trigger cascading faults if not resolved promptly.
ECM communication — J1939 network faults can affect all connected modules
Engine protection — ECM may trigger derate to prevent damage
Aftertreatment — engine protection derates can affect regen strategy
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.
Related Faults in This Category
OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 175 FMI 2 — 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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