Safe to driveEnough to reach the yard
J1939 code SPN 131. Below — how the fault is worded at the factory by KAMAZ, MAZ, Renault Trucks, YaMZ and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.
KAMAZMAZRenault TrucksYaMZZF AS-Tronic
| FMI 0 | Exhaust pipe pressure sensor: physical range limit |
| FMI 1 | Exhaust pipe pressure sensor: physical range limit |
| FMI 2 | Exhaust gas pressure sensor |
| FMI 3 | Exhaust gas pressure sensor |
| FMI 4 | Exhaust gas pressure sensor |
| FMI 2 | Exhaust pipe gas pressure sensor circuit fault - Plausibility error. Blink code: 3-4-5. Repair: Check the exhaust back pressure sensor and its wiring. |
| FMI 3 | Exhaust pipe gas pressure sensor circuit fault - Voltage above allowed. Blink code: 3-4-5. Repair: Check the exhaust back pressure sensor and its wiring. |
| FMI 4 | Exhaust pipe gas pressure sensor circuit fault - Voltage below allowed. Blink code: 3-4-5. Repair: Check the exhaust back pressure sensor and its wiring. |
| FMI 10 | Open circuit. Repair: Switch the ignition off, switch it on again and repeat the test. If the fault persists, replace the control unit. |
| FMI 2 | Exhaust pipe gas pressure sensor circuit fault (Plausibility error). Blink code: 3-4-5. Repair: Check the exhaust back pressure sensor and its wiring. |
| FMI 3 | Exhaust pipe gas pressure sensor circuit fault (Voltage above allowable limit). Blink code: 3-4-5. Repair: Check the exhaust back pressure sensor and its wiring. |
| FMI 4 | Exhaust pipe gas pressure sensor circuit fault (Voltage below allowable limit). Blink code: 3-4-5. Repair: Check the exhaust back pressure sensor and its wiring. |
ZF AS-Tronic uses its own fault numbering: the number in the table below is an internal ZF code, not a J1939 SPN. It matches the title of this page by digit only and means something different.
| FMI 10 | No signal from the shift sensor (main gearset). |
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.