Detroit Diesel SPN 3362 FMI 1 – DEF Pump Pressure Low (Meaning, Causes & Fix)

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Detroit Diesel SPN 3362 FMI 1 indicates that the DEF pump is not generating enough pressure to properly supply the dosing system. This code appears on DD13, DD15, and DD16 engines and means the SCR system cannot receive adequate DEF flow, which will affect emissions control and typically trigger a derate condition if left unresolved.

Symptoms

  • Check engine light on
  • DEF or SCR warning light illuminated
  • Engine derate condition
  • Reduced engine performance
  • SCR system unable to meet emissions thresholds
  • Possible low DEF flow related codes appearing together

Cause

This code triggers when the ECM detects DEF pump pressure falling below the minimum required threshold. Common causes include:

  • Worn or failing DEF pump
  • Low DEF level in tank
  • Air in the DEF supply lines
  • Clogged DEF filter restricting supply
  • DEF line leak reducing system pressure
  • Frozen DEF in cold weather conditions
  • Faulty DEF pressure sensor

Can You Keep Driving?

Limited driving is possible but without adequate DEF pump pressure the dosing system cannot supply DEF to the SCR catalyst. The engine will enter a derate condition if the fault is not addressed. Do not ignore this code.

Recommended Action

Start by checking the DEF tank level and refilling if low. Inspect the DEF filter and replace if clogged. Check DEF lines for leaks or air ingestion points. If the level and filter are good, have the DEF pump tested and replaced if it is not generating adequate pressure.

What does Detroit Diesel SPN 3362 FMI 1 mean?

It means the DEF pump is not generating enough pressure to supply the dosing system, preventing the SCR system from properly controlling NOx emissions.

What causes SPN 3362 FMI 1?

The most common causes are a worn or failing DEF pump, a clogged DEF filter, low DEF level, air in the supply lines, or a DEF line leak.

Can I keep driving with SPN 3362 FMI 1?

Short distances may be possible but the engine will derate if the DEF system cannot supply adequate pressure to the dosing injector.

Will SPN 3362 FMI 1 cause a derate?

Yes. Without sufficient DEF pump pressure the SCR system cannot function and the ECM will trigger a derate condition.

How do I clear SPN 3362 FMI 1?

Check DEF level and filter first. If those are good, have the DEF pump tested and replaced if necessary. Once the system confirms adequate pressure and proper dosing the code should clear.

Related codes

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Important Notice

The information provided above is for general informational purposes only and should not replace official OEM service procedures. Always consult the manufacturer’s service manual or a qualified diesel technician before performing repairs. Operating a vehicle with active fault codes may result in further damage.