Safe to driveTo the nearest safe stop
J1939 code SPN 1239. Below — how the fault is worded at the factory by Isuzu, and what the second half of the code (FMI) means in the standard.
| FMI 1 | No pump pressure feed (fuel leakage) (P0087) |
| SPN 1239 FMI 11239/1 · 1239.1 | data below normal range (most severe level) |
Safe to drive. Below — how much time you have and what happens if you keep going.
Fuel is not arriving in the right amount or at the right pressure. It shows up first on climbs and under load.
You will most likely stall out on the road, and may not restart on the shoulder. A clogged filter or water in the tank you can nurse to a shop; a failing injection pump you cannot.
That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.
Check the fuel filter and water trap, drain the water. In cold weather, suspect fuel waxing.
If the value really did go out of range, rather than a sensor circuit being broken, these normally light up after it:
They are not fixed separately — they go out together with this one. The list is deliberately short: only the links the reference is sure about.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.