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Fault Code Reference

SPN 1072 FMI 13AftertreatmentInducement Risk

SCR Intake NOx Sensor - Out of Calibration

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Overview

Fault Code

SPN 1072 / FMI 13

Category

Aftertreatment

Derate Risk

Yes

Regen Inhibit

No

Inducement Risk

Yes — SCR inducement possible

Component Location: SCR inlet NOx sensor is mounted on the exhaust inlet pipe of the SCR catalyst, typically on the mid-to-rear underside of the vehicle chassis near the aftertreatment assembly.

Common Symptoms

  • MIL or Check Engine Light illuminated
  • DEF consumption higher or lower than normal
  • NOx conversion efficiency fault codes may also be present
  • Poor SCR system performance
  • Emission test failure
  • Dosing system may increase DEF injection

Root Causes

  • NOx sensor calibration drift due to aging or heat exposure Contaminated or failed NOx sensor element Exhaust leak upstream of SCR inlet NOx sensor skewing readings Incorrect sensor part number or incompatible replacement sensor installed ACM software or calibration file mismatch requiring ECU reflash Sensor connector contamination or poor pin contact causing signal offset DEF dosing anomaly causing abnormal NOx baseline during calibration check Wiring harness damage causing intermittent signal corruption

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Derate Behavior

Power Derate

Yes

SCR Inducement Risk

If left unresolved, this fault may trigger SCR inducement — a progressive derate enforced by the ECM to ensure emissions compliance.

Mileage / Regen Notes

SPN 1072 FMI 13 may inhibit active DPF regeneration and can trigger SCR system derates; the ACM relies on SCR inlet NOx data to control DEF dosing, so an out-of-calibration sensor may cause incorrect dosing and prevent regen completion.

System Interactions

SPN 1072 FMI 13 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.

Deep-dive diagnostic page: SPN 1072 FMI 13 — 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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