Question 1

What does Cummins fault code 2962 mean?

Accepted Answer

2962 (Emissions): High Exhaust Temp / Derate Fix: LOGIC: EGR Temperature Above Normal (Severe).

ACTION: Check the EGR cooler for internal scaling or coolant flow restriction.

Question 2

What does Cummins fault code 3226-4 mean?

Accepted Answer

3226-4 (Emissions): Active Regen Inhibited Fix: LOGIC: Outlet NOx Sensor Voltage Below Normal.

ACTION: Inspect the sensor harness for a short to ground. Measure voltage at the 4-pin connector.

Question 3

What does Cummins fault code SPN 157 FMI 18 mean?

Accepted Answer

SPN 157 FMI 18 (Emissions): Derate (5 mph / 8 kph). The truck is restricted to "crawl" speed. Fix: DEF Pressure Too Low.

LOGIC: The aftertreatment system cannot build the required 5 bar (approx 72 psi) of DEF pressure.

ACTION: Check for frozen DEF lines in winter or a clogged DEF pump filter.

Question 4

What does Cummins fault code SPN 3216 FMI 3 mean?

Accepted Answer

SPN 3216 FMI 3 (Emissions): SCR Engine Derate / MIL On Fix: LOGIC: Aftertreatment 1 Intake NOx Sensor Circuit - Voltage Above Normal.

ACTION: Check for a melted sensor wiring harness near the exhaust pipe or a loose pin connection at the 4-pin plug.

Question 5

What does Cummins fault code SPN 3242 FMI 15 mean?

Accepted Answer

SPN 3242 FMI 15 (Emissions / DPF): Regen Aborted / High EGT Warning Fix: LOGIC: DPF Intake Gas Temperature High - Least Severe Level.

ACTION: Inspect DPF intake temperature sensor wiring for insulation burn damage. Check for unburned engine oil or raw fuel dumping into exhaust from turbo seal leakage or leaking fuel injector.

Question 6

What does Cummins fault code SPN 3251 FMI 00 mean?

Accepted Answer

SPN 3251 FMI 00 (Emissions / Exhaust): High Soot Level / Forced Regen Locked Fix: LOGIC: DPF Differential Pressure Very High (Severe).

ACTION: Measure delta pressure using a mechanical gauge to confirm high soot load. If actual pressure is high, remove DPF for off-machine thermal cleaning or replacement.

Question 7

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 8

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 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.

Cummins Fault Codes

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Code	System	Symptom	Full fix
2962	Emissions	High Exhaust Temp / Derate	View fix
3226-4	Emissions	Active Regen Inhibited	View fix
SPN 157 FMI 18	Emissions	Derate (5 mph / 8 kph). The truck is restricted to "crawl" speed.	View fix
SPN 3216 FMI 3	Emissions	SCR Engine Derate / MIL On	View fix
SPN 3242 FMI 15	Emissions / DPF	Regen Aborted / High EGT Warning	View fix
SPN 3251 FMI 00	Emissions / Exhaust	High Soot Level / Forced Regen Locked	View fix
SPN 3521 FMI 2	Emissions	Engine Derate / Check Engine Light	View fix
SPN 3521 FMI 2	Emissions	Derate / Check Engine Light	View fix
SPN 5246	Emissions	Active Final Inducement / Extreme Derate	View fix