SPN 2207 FMI 0Aftertreatment
NOx Sensor Circuit Intermittent Bank 1
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DVOM Testing — in guided session
Connector Pinout — in guided session
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Overview
Fault Code
SPN 2207 / FMI 0
Category
Aftertreatment
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: Upstream NOx sensor (Bank 1) is typically mounted on the exhaust pipe ahead of the SCR catalyst, near the turbocharger outlet or DOC/DPF assembly.
Common Symptoms
- DEF consumption higher than normal
- NOx sensor implausibility fault codes present
- Check engine light illuminated
- SCR efficiency monitoring disabled
- NOx reading fluctuating or erratic
- Intermittent high NOx values displayed
Root Causes
- Intermittent connector or terminal corrosion at NOx sensor harness connector
- Chafed or damaged NOx sensor wiring causing intermittent open or short
- Failed or degrading upstream (pre-SCR) NOx sensor
- Loose or poor ground connection at NOx sensor or ECM ground strap
- NOx sensor exposed to excessive heat causing intermittent internal failure
- Water intrusion into NOx sensor connector causing intermittent signal loss
- CAN communication fault between NOx sensor module and ECM
- ECM software or calibration issue causing false intermittent detection
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Derate Behavior
Power Derate
No
System Interactions
SPN 2207 FMI 0 interacts with the following systems and may trigger cascading faults if not resolved promptly.
DPF differential pressure monitoring — soot load calculations affected
SCR NOx conversion efficiency — DEF dosing strategy may be altered
Active regen inhibit logic — regen may be blocked or delayed
Engine protection derate — ECM may reduce power to protect components
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.
Replacing the DPF without verifying the regen system is functional — a failed regen injector will reload the new DPF.
Ignoring DEF quality — contaminated DEF causes SCR efficiency faults that look like hardware failures.
Related Faults in This Category
OEM System Resources
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Related Diagnostic Articles
Deep-dive diagnostic page: SPN 2207 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.
EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx 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.
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