Do not driveTo the nearest safe stop
J1939 code SPN 251. Below — how the fault is worded at the factory by DAF, Dongfeng, Meritor (ex-WABCO) and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.
DAFDongfengMeritor (ex-WABCO)ZF AS-Tronic
| FMI 2 | Real-time clock signal missing/implausible |
| FMI 2 | Invalid real-time clock data |
| FMI 10 | Real-time clock data not plausible (rate of change) |
| FMI 3 | ECU Main Ground or Reference Ground Connection — High Voltage |
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 0 | Internal expansion module (E-module) fault. |
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.