Safe to driveDrivable, but watch it yourself
J1939 code SPN 731. Below — how the fault is worded at the factory by SITRAK, and what the second half of the code (FMI) means in the standard.
| FMI 4 | Knock sensor 1 open circuit |
| FMI 15 | Knock retard reaches limit value |
| SPN 731 FMI 4731/4 · 731.4 | voltage below normal or shorted to ground |
| SPN 731 FMI 15731/15 · 731.15 | above normal — low severity |
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.