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SPN 175 FMI 4

Engine Oil Temperature 1 — Voltage below normal or shorted low.
The sensor circuit voltage is lower than it should ever be, usually near zero.

What the SPN covers: Temperature of the engine oil. More on SPN 175.

What FMI 4 usually points to: Signal wire shorted to ground, a lost 5 V reference, or an open signal wire on a pulled-down circuit. More on FMI 4.

Severity

HIGH — limit use, diagnose now

High oil temperature thins oil and can damage bearings. Reduce load and get it checked.

Likely causes

  1. Wiring or connector fault in this circuit (most common for electrical FMIs)
  2. Engine overloaded or overheating
  3. Plugged oil cooler
  4. Low oil level
  5. Sensor or wiring fault

Checks & fixes (easiest first)

  1. Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins
  2. Check the reference voltage, ground and signal at the component per OEM pin-out
  3. Check oil level and coolant temperature
  4. Inspect the oil cooler
  5. Compare sensor reading to coolant temp after warmup

FAQ

What does SPN 175 FMI 4 mean?

Engine Oil Temperature 1 — voltage below normal or shorted low. The sensor circuit voltage is lower than it should ever be, usually near zero.

Is SPN 175 FMI 4 serious?

High oil temperature thins oil and can damage bearings. Reduce load and get it checked.

What should I check first for SPN 175 FMI 4?

Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins; Check the reference voltage, ground and signal at the component per OEM pin-out; Check oil level and coolant temperature.