SPN 94 — Fuel delivery pressure
Safe to driveTo a stop or a shop
Updated: 2026-11-10
J1939 code SPN 94. Below — how the fault is worded at the factory by Foton, KAMAZ-5490 and Renault Trucks, and what the second half of the code (FMI) means in the standard.
How to check it yourself
Fuel pressure in the supply system: a pressure sensor (its location depends on the make). The unit uses it to see whether there is enough pressure for injection. Low pressure can cause loss of power and the engine stopping.
What it should read
| Fuel pressure at idle and under load | per the manufacturer's manual |
| Sensor signal with the engine off | neither zero nor at plus — per diagnostics |
Check order
- Pressure below normal: check the filters, the transfer pump and the air on the suction side (clear tube, bubbles); in winter, whether the fuel has waxed.
- FMI 3 or 4 (electrical): unplug the sensor connector and measure to plus and to ground with the ignition on.
- Pressure above normal: check the sensor and the pressure regulator; if it repeats — per the injection system troubleshooting guide.
Common causes — from most to least frequent
- Clogged fuel filters.
- In winter — wax in summer-grade fuel and a filter clogged by it.
- Air leak on the suction side.
- Transfer pump or pressure regulator.
- Pressure sensor or its connector.
Foton
| FMI 17 | Insufficient fuel pressure in Common Rail system |
KAMAZ-5490 (Mercedes, K-line)
FMI is per the block maker's own table, not the J1939 table below.
| FMI 0 | Fuel pressure: input shorted to high. |
| FMI 2 | Fuel pressure: signal out of range or implausible. |
| FMI 3 | Fuel pressure: open circuit. |
| FMI 4 | Fuel pressure: short to ground. |
Renault Trucks
| FMI 0 | Injection pressure above normal. Repair: Troubleshoot the injection system, check the sensor. |
| FMI 3 | Injection pressure sensor: short to +5 V or to battery voltage. Repair: Check the sensor and the engine wiring (A 6, A 13, A 33). |
| FMI 4 | Injection pressure sensor, short to ground. Repair: Check the sensor and the engine wiring (A 6, A 13, A 33). |
| FMI 18 | Injection pressure sensor, supply voltage too low. Repair: Check the sensor, the EECU and the engine wiring (A 6, A 13, A 33). |
What FMI means in J1939
Can I keep driving
You can drive to the nearest stop or a shop if power is normal. If power drops, the engine misfires or stalls — stop.
What happens if you keep driving
The fuel pressure is out of range, and the engine may not get enough fuel. It can show up as a loss of power and hesitation uphill and under load, and in a severe case the engine stopping.
If power is normal you can make it to the nearest stop or a shop; if power drops, the engine jerks or stops, stop. First check the fuel filters and air leaks on the suction side, and in winter fuel waxing.
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 the water trap, drain the water. In winter add fuel waxing to the suspects: summer-grade diesel in the cold and a filter clogged by it. If the FMI is 3 or 4 it is electrical: inspect the sensor connector and harness.
Which codes follow
If the value really did go out of range, rather than a sensor circuit being broken, these normally light up after it:
- SPN 652Engine Injector, Cylinder #02
- SPN 653Engine Injector, Cylinder #03
- SPN 655Engine Injector, Cylinder #05
- SPN 1569Torque limited (engine protection)
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.
Nearby: fuel
- SPN 38Fuel Level, Secondary Tank
- SPN 97Water in fuel indicator
- SPN 157Injector Metering Rail Pressure #1
- SPN 164Injection Control Pressure
- SPN 652Engine Injector, Cylinder #02
- SPN 653Engine Injector, Cylinder #03
- SPN 655Engine Injector, Cylinder #05
- SPN 1347Fuel Delivery Pump Assembly #1
Makes with this code
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.