Do not driveTo the nearest safe stop
SPN 520224 is a manufacturer number outside the standard J1939 table: different makes can put different things under it. Below — how it is worded by KAMAZ, MAZ, SITRAK, Volvo and YaMZ, and what the second half of the code (FMI) means.
| FMI 0 | Air humidity sensor: physical range limit |
| FMI 1 | Air humidity sensor: physical range limit |
| FMI 3 | Air humidity sensor |
| FMI 4 | Air humidity sensor |
| FMI 3 | Humidity sensor fault - Reading above allowed. Blink code: 2-3-6. Repair: Check the humidity sensor and its wiring. |
| FMI 4 | Humidity sensor fault - Reading below allowed. Blink code: 2-3-6. Repair: Check the humidity sensor and its wiring. |
| FMI 11 | ECU internal monitoring reported a fault, function monitoring level (MoF). Scan tool code: P1012. |
| FMI 12 | Light switch pulled for more than 60 seconds. Switch damaged, or wiring between the LCM and the switch shorted to ground. |
| FMI 3 | Humidity sensor fault (Reading above allowable limit). Blink code: 2-3-6. Repair: Check the humidity sensor and its wiring. |
| FMI 4 | Humidity sensor fault (Reading below allowable limit). Blink code: 2-3-6. Repair: Check the humidity sensor and its wiring. |
Do not drive. Stop as soon as it’s safe to do so — don’t keep going.
The code is flagged critical: the manufacturer considers it unsafe to keep driving without checking.
This code alone cannot say what will fail next, so stop at the first safe opportunity and look at it on the spot.
That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.