SPN 4072 FMI 16Aftertreatment
Aftertreatment 1 Purge Air Actuator - Data Valid But Above Normal
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Overview
Fault Code
SPN 4072 / FMI 16
Category
Aftertreatment
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: The purge air actuator is mounted on the aftertreatment housing to supply compressed air for DPF cleaning cycles.
Common Symptoms
- Check engine light illuminated
- Active fault code SPN 4072 FMI 16
- Aftertreatment purge air actuator position higher than commanded
- Possible failed parked regeneration
- Excessive purge air flow during active regeneration
- Hydrocarbon doser performance issues
Root Causes
- Purge air actuator valve stuck open or operating outside normal range
- Restricted or blocked purge air supply line causing abnormal pressure feedback
- Faulty purge air actuator with internal leakage or mechanical failure
- ACM software or calibration issue causing incorrect commanded vs. actual position
- Wiring short to voltage on actuator control or feedback circuit
- Failed or degraded purge air actuator position sensor
- Air supply pressure to actuator above spec due to faulty regulator
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Derate Behavior
Power Derate
No
Mileage / Regen Notes
An above-normal purge air actuator signal may inhibit or interrupt active DPF regeneration cycles, as the ACM may detect abnormal purge air flow conditions and prevent or abort regen to protect aftertreatment components.
System Interactions
SPN 4072 FMI 16 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 4072 FMI 16 — 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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