Safe to driveDrivable, but watch it yourself
SPN 4039 is a manufacturer number outside the standard J1939 table: different makes can put different things under it. Below — how it is worded by International, Knorr-Bremse EBS and MAN, and what the second half of the code (FMI) means.
InternationalKnorr-Bremse EBSMAN
| FMI 5 | Snow Plow Forward Lighting Relay 1 — Left Plow Light Relay Circuit Under Current Or Open Circuit |
| FMI 6 | Snow Plow Forward Lighting Relay 1 — Left Plow Light Relay Circuit Short To Ground |
| FMI 3 | Central control unit, EEPROM unknown value ESP. Not identified |
| FMI 3 | Central control unit EEPROM ESP configuration - Not identified |
| SPN 4039 FMI 34039/3 · 4039.3 | voltage above normal or shorted high |
| SPN 4039 FMI 54039/5 · 4039.5 | current below normal or open circuit |
| SPN 4039 FMI 64039/6 · 4039.6 | current above normal or grounded 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.