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SPN 38 — Fuel Level, Secondary Tank

Safe to driveTo the nearest safe stop

J1939 code SPN 38. Below — how the fault is worded at the factory by SITRAK and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.

SITRAK

FMI 3Fuel level sensor voltage above the upper limit. Scan tool code: P0460. Effect: Power limited, the engine runs unevenly.
FMI 4Fuel level sensor voltage below the lower limit. Scan tool code: P0460. Effect: Power limited, the engine runs unevenly.
FMI 19Fuel level signal error on the CAN bus. Effect: Loss of communication with the modules, some functions are disabled.

ZF AS-Tronic

ZF AS-Tronic uses its own fault numbering: the number in the table below is an internal ZF code, not a J1939 SPN. It matches the title of this page by digit only and means something different.

FMI 10Fault on valve Y6 output circuit (engagement valve).

What FMI means in J1939

SPN 38 FMI 338/3 · 38.3voltage above normal or shorted high
SPN 38 FMI 438/4 · 38.4voltage below normal or shorted to ground
SPN 38 FMI 1038/10 · 38.10abnormal rate of change
SPN 38 FMI 1938/19 · 38.19error in received network data

Can I keep driving

Safe to drive. Below — how much time you have and what happens if you keep going.

What happens if you keep driving

Time you have: To the nearest safe stop

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.

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.

What to check on the spot

Check the fuel filter and water trap, drain the water. In cold weather, suspect fuel waxing.

Nearby: fuel

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