Safe to driveEnough to reach the yard
J1939 code SPN 3226. Below — how the fault is worded at the factory by DAF, Dongfeng and SITRAK, and what the second half of the code (FMI) means in the standard.
| FMI 0 | NOx sensor F791 NOx value very high (extended period) |
| FMI 2 | NOx sensor F791 signal missing/implausible (extended period) |
| FMI 4 | NOx sensor F791 internal error (extended period) |
| FMI 9 | NOx sensor F791 CAN network communication error (extended period) |
| FMI 15 | NOx sensor F791 NOx value too high (extended period) |
| FMI 20 | NOx sensor F791 internal error (extended period) |
| FMI 31 | NOx sensor F791 incorrect power supply (extended period) |
| FMI 0 | NOx emissions exceed 2nd OBD limit |
| FMI 2 | NOx concentration implausibly low |
| FMI 4 | Internal malfunction of the inlet NOx sensor |
| FMI 9 | Timeout of a message from the outlet NOx sensor |
| FMI 15 | NOx emissions exceed 1st OBD limit. Scan tool code: P2201. |
| FMI 15 | NOx sensor reading too high. Scan tool code: P2201. |
| FMI 17 | NOx sensor reading too low. Scan tool code: P2201. |
| FMI 19 | Incorrect data length of the AT1OG1 CAN frame. Effect: Torque may be limited. |
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.
That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.
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:
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.