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SPN 174 FMI 16

Engine Fuel Temperature 1 — Value too high (moderately severe).
The reading is above normal at a middle warning level — more serious than FMI 15, less than FMI 0.

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 16 usually points to: A developing over-condition that often precedes a derate. More on FMI 16.

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 16 mean?

Engine Fuel Temperature 1 — value too high (moderately severe). The reading is above normal at a middle warning level — more serious than FMI 15, less than FMI 0.

Is SPN 174 FMI 16 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 16?

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.