Do not driveTo the nearest safe stop
J1939 code SPN 78. Below — how the fault is worded at the factory by International and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.
| FMI 0 | Rear Rear Drive Axle Temperature — Rear Rear Axle Temperature Sensor reading above normal range |
| FMI 1 | Rear Rear Drive Axle Temperature — Rear Rear Axle Temperature Sensor reading below normal range |
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 | Short circuit to positive supply on the ZF E-module output connected to power take-off 2 (PTO2). |
| SPN 78 FMI 078/0 · 78.0 | data above normal range (most severe level) |
| SPN 78 FMI 178/1 · 78.1 | data below normal range (most severe level) |
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.