Safe to driveEnough to reach the yard
J1939 code SPN 1235. Below — how the fault is worded at the factory by KAMAZ, MAZ and YaMZ, and what the second half of the code (FMI) means in the standard.
| FMI 12 | ⚠ CAN bus C off-line (bus-off) |
| FMI 12 | CAN line C missing - Bus disconnected. Blink code: 4-1-3. Repair: Check the CAN bus connection to the other CAN devices. |
| FMI 12 | CAN line C missing (Bus disconnected). Blink code: 4-1-3. Repair: Check the CAN bus connection to the other CAN devices. |
| SPN 1235 FMI 121235/12 · 1235.12 | faulty device or component |
Safe to drive. Below — how much time you have and what happens if you keep going.
The modules have stopped hearing each other on the bus. Some dash readings are now made up and some functions are simply off.
You can physically drive, but do not trust the instruments, and the other codes in the list may well be false: fix the bus first, then look at the rest.
Check connectors and the harness: a broken CAN twisted pair takes out communication for every ECU at once.
These normally light up after this code:
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.