Safe to driveEnough to reach the yard
J1939 code SPN 3251. Below — how the fault is worded at the factory by Foton and SITRAK, and what the second half of the code (FMI) means in the standard.
| FMI 15 | Insufficient AdBlue system pressure |
| FMI 3 | DPF differential pressure sensor voltage above the upper limit. Scan tool code: P2452. Effect: Torque may be limited. |
| FMI 4 | DPF differential pressure sensor voltage below the lower limit. Scan tool code: P2452. Effect: Torque may be limited. |
| FMI 20 | Learned offset of the differential pressure sensor deviates too much between two consecutive driving cycles. Scan tool code: P244B. Effect: Torque limited, the engine may shut down. |
Safe to drive. Below — how much time you have and what happens if you keep going.
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.
Fill the AdBlue tank. If it’s already full, the problem is dosing or reductant quality — you need a scanner.
This code is often not the fault itself but a knock-on. If any of these is in the same readout, start with it:
If the value really did go out of range, rather than a sensor circuit being broken, these normally light up after it:
They are not fixed separately — they go out together with this one. The list is deliberately short: only the links the reference is sure about.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.