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SPN 105 FMI 15

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

What the SPN covers: Temperature of the air entering the cylinders after the charge air cooler. More on SPN 105.

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

High intake temps reduce power and can lead to a derate. Drivable with care.

Likely causes

  1. Dirty or blocked charge-air cooler fins
  2. Charge-air cooler leak
  3. Fan not engaging
  4. EGR cooler problem raising intake temperature
  5. Sensor or wiring fault

Checks & fixes (easiest first)

  1. Clean the CAC and radiator stack
  2. Verify fan engagement
  3. Pressure-test the CAC
  4. Compare the sensor to ambient after a cold soak

FAQ

What does SPN 105 FMI 15 mean?

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

Is SPN 105 FMI 15 serious?

High intake temps reduce power and can lead to a derate. Drivable with care.

What should I check first for SPN 105 FMI 15?

Clean the CAC and radiator stack; Verify fan engagement; Pressure-test the CAC.