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SPN 3050 — Catalyst System Monitor 1

Safe to driveEnough to reach the yard

J1939 code SPN 3050. Below — how the fault is worded at the factory by DAF, MAZ, SITRAK and YaMZ, and what the second half of the code (FMI) means in the standard.

DAFMAZSITRAKYaMZ

DAF

FMI 0Catalyst temperature F765/F766 temperature too high (extended period)
FMI 31Catalyst temperature F765/F766 not detected (extended period)

MAZ

FMI 0DPF blocked - Voltage above allowed. Blink code: 6-1-5. Repair: Check the aftertreatment filter.
FMI 1DPF removed - Voltage above allowed. Blink code: 6-1-7. Repair: Regenerate the aftertreatment filter.
FMI 3DPF differential pressure sensor error - Voltage above allowed. Blink code: 6-1-6. Repair: Check the aftertreatment filter differential pressure sensor and its wiring.
FMI 4DPF differential pressure sensor error - Voltage below allowed. Blink code: 6-1-6. Repair: Check the aftertreatment filter differential pressure sensor and its wiring.
FMI 12DPF differential pressure sensor error - CAN bus signal implausible. Blink code: 6-1-6. Repair: Check the aftertreatment filter differential pressure sensor and its wiring.

SITRAK

FMI 11Three-way catalyst oxygen storage capacity monitor

YaMZ

FMI 0Particulate filter blocked (Voltage above allowable limit). Blink code: 6-1-5. Repair: Check the aftertreatment filter.
FMI 1Particulate filter removed (Voltage above allowable limit). Blink code: 6-1-7. Repair: Regenerate the aftertreatment filter.
FMI 3Particulate filter differential pressure sensor fault (Voltage above allowable limit). Blink code: 6-1-6. Repair: Check the aftertreatment filter differential pressure sensor and its wiring.
FMI 4Particulate filter differential pressure sensor fault (Voltage below allowable limit). Blink code: 6-1-6. Repair: Check the aftertreatment filter differential pressure sensor and its wiring.
FMI 12Particulate filter differential pressure sensor fault (CAN bus signal implausible). Blink code: 6-1-6. Repair: Check the aftertreatment filter differential pressure sensor and its wiring.

What FMI means in J1939

SPN 3050 FMI 03050/0 · 3050.0data above normal range (most severe level)
SPN 3050 FMI 13050/1 · 3050.1data below normal range (most severe level)
SPN 3050 FMI 33050/3 · 3050.3voltage above normal or shorted high
SPN 3050 FMI 43050/4 · 3050.4voltage below normal or shorted to ground
SPN 3050 FMI 113050/11 · 3050.11root cause not known
SPN 3050 FMI 123050/12 · 3050.12faulty device or component
SPN 3050 FMI 313050/31 · 3050.31condition exists (see manufacturer description)

Can I keep driving

Safe to drive. Below — how much time you have and what happens if you keep going.

What happens if you keep driving

Time you have: Enough to reach the yard

Urea dosing is interrupted and the ECU is counting. First the lamp, then a torque cut, then a forced crawl speed — the stages come in by engine hours, not all at once.

The truck will not die mid-highway, but the window shrinks with every running hour. Plan the repair now, not when the power is gone: an emulator or "deleting AdBlue" does not remove the problem, the codes keep stacking.

That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.

What to check on the spot

Fill the AdBlue tank. If it’s already full, the problem is dosing or reductant quality — you need a scanner.

Nearby: AdBlue / exhaust

Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.