Safe to driveDrivable, but watch it yourself
SPN 520644 is a manufacturer number outside the standard J1939 table: different makes can put different things under it. Below — how it is worded by International, and what the second half of the code (FMI) means.
| FMI 3 | PPE3 AC Module Input Voltage — AC Module Overvoltage condition on High Voltage DC Bus. |
| FMI 4 | PPE3 AC Module Input Voltage — AC Module Undervoltage condition on High Voltage DC Bus. |
| SPN 520644 FMI 3520644/3 · 520644.3 | voltage above normal or shorted high |
| SPN 520644 FMI 4520644/4 · 520644.4 | 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.