Do not driveTo the nearest safe stop
J1939 code SPN 77. Below — how the fault is worded at the factory by International, Renault Trucks and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.
InternationalRenault TrucksZF AS-Tronic
| FMI 0 | Forward Rear Drive Axle Temperature — Front Rear Axle Temperature Sensor reading above normal range |
| FMI 1 | Forward Rear Drive Axle Temperature — Front Rear Axle Temperature Sensor reading below normal range |
| FMI 6 | Short to battery positive. Repair: Check the power take-off solenoid valve (40 ohms < R < 50 ohms). Check the wiring between the Astronic and the component (X1A/10). Switch the ignition off, switch it on again and repeat the test. If the fault persists, replace the control unit. |
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 1 (PTO1). |
| SPN 77 FMI 077/0 · 77.0 | data above normal range (most severe level) |
| SPN 77 FMI 177/1 · 77.1 | data below normal range (most severe level) |
| SPN 77 FMI 677/6 · 77.6 | current above normal or grounded circuit |
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.