What are the symptoms of SPN 2659 FMI 2?

EGR mass flow reading erratic or jumping in live data. Engine derate active - ECM cannot reliably control EGR flow. Possible black smoke under load - EGR flow uncontrolled. Intermittent fault - sets and clears with temperature or vibration changes. Possible companion faults: SPN 411/31 (EGR differential pressure), SPN 2659/0 (EGR flow high)

What causes SPN 2659 FMI 2?

EGR mass flow sensor connector - loose, corroded, or intermittent connection. EGR mass flow sensor wiring harness - chafed or broken wire causing intermittent signal. EGR mass flow sensor failure - sensor element contaminated with soot or oil. EGR differential pressure sensor fault - erratic differential pressure causes erratic flow calculation. EGR valve position sensor fault - erratic valve position causes erratic flow reading. Exhaust vibration causing intermittent sensor connector contact

How do I diagnose SPN 2659 FMI 2?

Full step-by-step DVOM tests, electrical procedures, and connector pinout data for SPN 2659 FMI 2 are available inside the AI Diesel Tech guided diagnostic session. The AI walks you through every test — one step at a time.

SPN 2659 FMI 2EGR SystemHigh

EGR Mass Flow Rate - Data Erratic, Intermittent or Incorrect

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Overview

Fault Code

SPN 2659 / FMI 2

Common Symptoms

EGR mass flow reading erratic or jumping in live data
Engine derate active - ECM cannot reliably control EGR flow
Possible black smoke under load - EGR flow uncontrolled
Intermittent fault - sets and clears with temperature or vibration changes
Possible companion faults: SPN 411/31 (EGR differential pressure), SPN 2659/0 (EGR flow high)

Root Causes

EGR mass flow sensor connector - loose, corroded, or intermittent connection
EGR mass flow sensor wiring harness - chafed or broken wire causing intermittent signal
EGR mass flow sensor failure - sensor element contaminated with soot or oil
EGR differential pressure sensor fault - erratic differential pressure causes erratic flow calculation
EGR valve position sensor fault - erratic valve position causes erratic flow reading
Exhaust vibration causing intermittent sensor connector contact

Full step-by-step tests, DVOM guidance, and pinout data are available inside the AI Diesel Tech diagnostic session.

AI walks you through every test — one step at a time. Plans start at $12.95/mo.

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Derate Behavior

Power Derate

Yes

Mileage / Regen Notes

EGR sensor contamination increases with mileage. Connector wear increases with heat cycling and vibration.

System Interactions

SPN 2659 FMI 2 interacts with the following systems and may trigger cascading faults if not resolved promptly.

TSB Reference: Cummins TSB 4021889 - EGR Mass Flow Sensor Diagnosis; Detroit TSB 17-015 - EGR System Erratic Signal Diagnosis

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.

OEM Notes

Cummins

X15: EGR mass flow sensor soot contamination is common - clean sensor before replacing. INSITE EGR system test required.

Detroit

DD15: EGR mass flow sensor connector is exposed to heat and vibration - connector wear is common. DDDL EGR system test required.

PACCAR

MX-13: EGR differential pressure sensor fault often causes erratic EGR flow reading - check differential pressure sensor first. DAVIE4 EGR test required.

Volvo

MP8: EGR mass flow sensor failure is common at 400k+ miles on MP8. PTT EGR system test required.