Question 1

What does Cummins fault code SPN 3364 (FMI 9/19) mean?

Accepted Answer

SPN 3364 (FMI 9/19) (Exhaust (SCR)): Inducement / Engine Derate. Fix: LOGIC: Abnormal Update Rate (CAN Comm Error) to the DEF Quality Sensor.

ACTION: Check the 4-pin plug at the DEF Header. Verify 12V/24V power and CAN-Hi/Low (60 Ohms).

Question 2

What does Cummins fault code SPN 343 FMI 12 mean?

Accepted Answer

SPN 343 FMI 12 (Electrical): ECM Hardware Failure. Fix: LOGIC: Internal ECM memory error (EEPROM).

ACTION: Disconnect batteries for 30 mins to "Hard Reset." If it returns, the ECM requires a re-flash or replacement.

Question 3

What does Cummins fault code SPN 3509 FMI 3 mean?

Accepted Answer

SPN 3509 FMI 3 (Sensors): Multiple Sensor Errors Fix: LOGIC: Sensor Supply Voltage 1 - Voltage Above Normal.

ACTION: Check for a short between the 5V reference wire and the 12V/24V power wire in the harness.

Question 4

What does Cummins fault code SPN 3521 FMI 0 mean?

Accepted Answer

SPN 3521 FMI 0: Low Power. Fix: LOGIC: SCR Catalyst Conversion Efficiency Low.

ACTION: Verify DEF quality with a refractometer; check NOx sensors for drift using Insite.

Question 5

What does Cummins fault code SPN 3521 FMI 2 mean?

Accepted Answer

SPN 3521 FMI 2 (Emissions): Derate / Check Engine Light Fix: LOGIC: SCR Catalyst Conversion Efficiency Erratic/Incorrect.

ACTION: Inspect DEF doser injector for crystallization/clogging. Sample DEF quality with a refractometer (must read 32.5% concentration).

Question 6

What does Cummins fault code SPN 3521 FMI 2 mean?

Accepted Answer

SPN 3521 FMI 2 (Emissions): Engine Derate / Check Engine Light Fix: LOGIC: SCR Catalyst Conversion Efficiency Erratic/Incorrect.

ACTION: Inspect DEF doser injector for crystallization/clogging. Sample DEF quality with a refractometer (must read 32.5% concentration).

Question 7

What does Cummins fault code SPN 3719 FMI 15 mean?

Accepted Answer

SPN 3719 FMI 15 (Aftertreatment): Regen Required Soon Fix: LOGIC: DPF Soot Load High (Level 1).

ACTION: Advise operator to keep engine RPM high or perform a "Parked Regen" immediately.

Question 8

What does Cummins fault code SPN 4334 FMI 16 mean?

Accepted Answer

SPN 4334 FMI 16 (Aftertreatment): DEF Pressure High / Derate. Fix: LOGIC: DEF Dosing pressure is above the threshold.

ACTION: Check for a kinked or frozen DEF return line. If lines are clear, inspect the DEF injector for a nozzle blockage.

Question 9

What does Cummins fault code SPN 5246 mean?

Accepted Answer

SPN 5246 (Emissions): Active Final Inducement / Extreme Derate Fix: LOGIC: Regulatory Feedthrift Derate Active.

ACTION: Check SCR efficiency, DEF quality, or for active SCR dosing system blockages. Force a deep stationary regeneration.

Question 10

What does Cummins fault code SPN 5246 FMI 0 mean?

Accepted Answer

SPN 5246 FMI 0 (Exhaust): 5-MPH Derate Active. Fix: LOGIC: Aftertreatment Regulatory Derate.

ACTION: Perform a Forced Regen. If it fails, check for a "Face Plugged" DPF.

Code	System	Symptom	Full fix
SPN 3364 (FMI 9/19)	Exhaust (SCR)	Inducement / Engine Derate.	View fix
SPN 343 FMI 12	Electrical	ECM Hardware Failure.	View fix
SPN 3509 FMI 3	Sensors	Multiple Sensor Errors	View fix
SPN 3521 FMI 0	—	Low Power.	View fix
SPN 3521 FMI 2	Emissions	Derate / Check Engine Light	View fix
SPN 3521 FMI 2	Emissions	Engine Derate / Check Engine Light	View fix
SPN 3719 FMI 15	Aftertreatment	Regen Required Soon	View fix
SPN 4334 FMI 16	Aftertreatment	DEF Pressure High / Derate.	View fix
SPN 5246	Emissions	Active Final Inducement / Extreme Derate	View fix
SPN 5246 FMI 0	Exhaust	5-MPH Derate Active.	View fix
SPN 5246 FMI 15	Aftertreatment	Derate (Speed limited to 5 mph)	View fix
SPN 641 FMI 7	Air Intake	Low Boost / Sluggish Acceleration	View fix
SPN 641 FMI 7	Air Intake	Low Boost / Heavy Sluggish Pick-up	View fix
SPN 641 FMI 9	—	Turbo boost is stuck or erratic; Engine feels underpowered; No turbo "spool" sound; Active stop lamp.	View fix
SPN: 3582 FMI: 2	Aftertreatment	SCR System Fault / Derate.	View fix

Cummins Fault Codes