Safe to driveDrivable, but watch it yourself
J1939 code SPN 3855. 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 3 | Digital Input 2/14 Circuit shorted to Ubat |
| FMI 4 | Digital Input 2/14 Circuit shorted to GND |
| SPN 3855 FMI 33855/3 · 3855.3 | voltage above normal or shorted high |
| SPN 3855 FMI 43855/4 · 3855.4 | voltage below normal or shorted to ground |
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.