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SPN 174 FMI 15

Engine Fuel Temperature 1 — Value too high (least severe).
The reading is above normal, but only at the lowest warning level.

What the SPN covers: Temperature of the fuel in the injection system. The engine computer uses it to correct fueling and may derate to protect the pump and injectors when fuel runs hot. More on SPN 174.

What FMI 15 usually points to: An early warning: mild over-temperature or over-pressure, or a sensor starting to drift high. More on FMI 15.

Severity

MEDIUM — fix soon

Hot fuel lowers power and can damage the pump and injectors. Usually drivable carefully, but find out why it's hot.

Likely causes

  1. Running with a low tank in hot weather (little fuel to absorb return heat)
  2. Restricted or missing fuel cooler airflow
  3. High return flow from a leaking injector, relief valve or pump
  4. Fuel temperature sensor or wiring fault

Checks & fixes (easiest first)

  1. Fill the tank and recheck the reading
  2. Inspect the fuel cooler (if fitted) for debris and damage
  3. Measure injector and pump return flow per OEM
  4. Compare the sensor with an infrared reading and check its circuit

Troubleshooting guides

FAQ

What does SPN 174 FMI 15 mean?

Engine Fuel Temperature 1 — value too high (least severe). The reading is above normal, but only at the lowest warning level.

Is SPN 174 FMI 15 serious?

Hot fuel lowers power and can damage the pump and injectors. Usually drivable carefully, but find out why it's hot.

What should I check first for SPN 174 FMI 15?

Fill the tank and recheck the reading; Inspect the fuel cooler (if fitted) for debris and damage; Measure injector and pump return flow per OEM.