Safe to driveDrivable, but watch it yourself
J1939 code SPN 924. Below — how the fault is worded at the factory by Mercedes-Benz and Renault Trucks, and what the second half of the code (FMI) means in the standard.
| FMI 3 | Digital Output 4/09 Circuit shorted to Ubat |
| FMI 4 | Digital Output 4/09 Circuit shorted to GND |
| FMI 5 | Digital Output 4/09 Open Circuit (broken wire, terminal floating) |
| FMI 3 | M, H, K — low speed output; P — Austeras output. Short to positive. Repair: Check the continuity and insulation of the wiring with respect to +24 V (SL2/8). |
| FMI 4 | M, H, K — low speed output; P — Austeras output. Open circuit or short to ground. Repair: Check the continuity and insulation of the wiring with respect to ground (SL2/8). |
| SPN 924 FMI 3924/3 · 924.3 | voltage above normal or shorted high |
| SPN 924 FMI 4924/4 · 924.4 | voltage below normal or shorted to ground |
| SPN 924 FMI 5924/5 · 924.5 | current below normal or open circuit |
Safe to drive. Below — how much time you have and what happens if you keep going.
This is an electrical fault: an open, a short or a bad contact in the sensor circuit. The value it measures is most likely fine.
You can drive. But until the circuit is repaired this system runs blind and cannot warn you about a real failure.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.