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SPN 174 FMI 2

Engine Fuel Temperature 1 — Data erratic, intermittent, or incorrect.
The signal jumps around, drops in and out, or disagrees with other information the controller has.

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 2 usually points to: Loose or corroded connectors, chafed wiring, a failing sensor, or two redundant sensors that do not agree. More on FMI 2.

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 2 mean?

Engine Fuel Temperature 1 — data erratic, intermittent, or incorrect. The signal jumps around, drops in and out, or disagrees with other information the controller has.

Is SPN 174 FMI 2 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 2?

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.