SPN 4792 FMI 31EGR
EGR Temperature Sensor - Condition Exists
Scan Tool — in guided session
DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 4792 / FMI 31
Category
EGR
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: EGR temperature sensor is typically mounted on the EGR cooler outlet or EGR mixer inlet on the engine, accessible from the top or side of the engine block.
Common Symptoms
- Check engine light illuminated
- EGR system monitoring fault active
- Reduced engine performance or throttle response
- Increased NOx emissions
- EGR cooler efficiency concern flagged
Root Causes
- EGR cooler fouling or soot buildup causing abnormal temperature readings
- Failed or drifted EGR temperature sensor
- EGR valve stuck open or closed causing abnormal exhaust gas flow
- EGR cooler internal failure or coolant leak affecting temperature
- Wiring harness damage, chafing, or corrosion at EGR temperature sensor connector
- ECM software or calibration issue triggering condition exists fault
- High exhaust backpressure from plugged DPF affecting EGR temperatures
- Faulty ECM or sensor reference voltage issue
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Derate Behavior
Power Derate
No
Mileage / Regen Notes
SPN 4792 FMI 31 may inhibit or delay active DPF regeneration if EGR system temperature faults are present, as the ECM uses EGR temperature data to manage exhaust thermal conditions during regen. Severe EGR faults can result in regen lockout.
System Interactions
SPN 4792 FMI 31 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.
Related Faults in This Category
OEM System Resources
ASE Training Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 4792 FMI 31 — 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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