Safe to driveTo the nearest safe stop
J1939 code SPN 523. Below — how the fault is worded at the factory by Mercedes-Benz, and what the second half of the code (FMI) means in the standard.
| FMI 13 | Transmission Current Gear Signal Missing |
| FMI 19 | Transmission Current Gear Signal Erratic |
| SPN 523 FMI 13523/13 · 523.13 | calibration out of range |
| SPN 523 FMI 19523/19 · 523.19 | error in received network data |
Safe to drive. Below — how much time you have and what happens if you keep going.
The gearbox or clutch has gone into limp mode: some gears may be unavailable and an automated box may stop shifting under load.
The main risk is being left on a climb with no gear and rolling back. Do not take a loaded truck into the hills; reaching level ground and a shop is fine.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.