Truck Fault Codes

Volvo D13 SPN 3361 FMI 1 �?DEF Supply Pressure Below Normal

SPN 3361 FMI 1 on a Volvo D13 means DEF supply pressure is below normal. Connect VCADS Pro or JPRO to check the DEF pump supply pressure commanded and actual values. Inspect the DEF filter for restriction, check the supply lines for blockage or freeze, and confirm DEF quality and level. If the filter and lines are clear and pressure is still low, the DEF pump module requires testing.

Code Details

Structured details for SPN 3361 FMI 1
Display codeSPN 3361 FMI 1
SPN3361
FMI1
OEM codeNone listed
ManufacturerVolvo
SystemAftertreatment �?DEF supply system
ComponentDEF supply pump / DEF tank module / filter / lines
Source addressUnknown or not applicable
Severitymedium
Review statussource backed
Source confidencemedium
Last reviewed2026-06-11

Plain-English Meaning

The Volvo D13 SCR system requires DEF to be delivered under pressure to the dosing injector. The DEF supply pump in the tank module draws fluid from the tank and maintains the required supply pressure. When this pressure falls below the normal threshold, DEF dosing becomes inadequate and SCR efficiency declines. Possible causes include a clogged filter, frozen lines in cold weather, or a pump that is losing output.

SPN 3361 FMI 1 is Aftertreatment DEF Dosing Unit Pressure below normal range. On Volvo D13 with the UECU (aftertreatment control unit), VCADS Pro monitors DEF supply pressure, pump duty cycle, DEF temperature, and DEF quality. VCADS Pro can also run a DEF pump pressure test by commanding the pump and monitoring whether it achieves and holds the target pressure.

Common Symptoms

  • DEF level or quality warning displayed alongside pressure warning
  • SCR efficiency fault may follow if DEF dosing is insufficient
  • In cold weather, may occur at startup before the DEF system heater cycle completes

Possible Causes

Possible causes may include the items below. The list is not a parts diagnosis.

  • Clogged DEF supply filter in the tank module
  • DEF supply line blocked or partially frozen
  • Worn or failing DEF supply pump
  • DEF supply pressure sensor fault
  • DEF tank level critically low

First Checks

  • Connect VCADS Pro and run the DEF pump pressure test to compare commanded and actual output
  • Replace the DEF supply filter if at or past service interval
  • Check all DEF supply line connections for kinks, cracks, or blockage
  • In cold weather, wait for the full DEF system warm-up cycle to complete before drawing conclusions

Can I Keep Driving?

Driveable. Persistent low DEF supply pressure will reduce SCR efficiency and may trigger the inducement sequence. Repair promptly.

SPN 5246 FMI 31Aftertreatment �?SCR system · SCR catalyst / NOx sensorsSPN 3364 FMI 1Aftertreatment �?DEF system · DEF quality / concentration sensor

Related Lookup Pages

Sources

  • Volvo Trucks Tech Info Public Resources Volvo Trucks North America · oem · accessed 2026-06-11 · confidence medium

    Source: Volvo Trucks North America, Volvo Trucks Tech Info Public Resources. This page paraphrases factual fields only and is not a substitute for the original document.

    Open source
  • Volvo Trucks / Mack Trucks Technical Support Volvo Trucks North America / Mack Trucks Inc. · oem · accessed 2026-06-10 · confidence medium

    Source: Volvo Trucks North America / Mack Trucks Inc., Volvo Trucks / Mack Trucks Technical Support. This page paraphrases factual fields only and is not a substitute for the original document.

    Open source
  • SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium

    Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.

    Open source

FAQ

Does the Volvo D13 DEF pump have a separate pressure regulator that could cause this fault?

The Volvo D13 DEF system uses a pump and pressure regulation circuit within the DEF tank module. The pressure regulator is not typically a separately serviceable part �?it is integrated into the module. If the pump output is confirmed weak via VCADS Pro testing with a new filter and clear lines, the entire DEF tank module (pump, regulator, level sensor, quality sensor, heater) is typically replaced as a unit.

Can the Volvo D13 DEF system prime itself after running out of DEF?

After the DEF tank runs dry, the pump must re-prime the supply lines before dosing can resume. VCADS Pro can initiate a prime cycle to speed the process. In some cases if air is trapped in the lines after running dry, a manual prime using VCADS Pro is needed before the system will return to normal operation. Always check for and clear any DEF quality or dosing faults after refilling after a run-dry event.

Is the DEF tank module on the Volvo D13 the same as on the Mack MP8?

The Volvo D13 and Mack MP8 share significant platform and aftertreatment hardware. In many configurations, the DEF tank module is the same part across the Volvo D13 and Mack MP8. Confirm via VCADS Pro parts look-up or the Volvo or Mack parts portal for the specific model year and aftertreatment package installed.