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SPN 101 FMI 16

Engine Crankcase Pressure — 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: Gas pressure inside the crankcase, usually measured at or near the crankcase ventilation (CCV) filter. Rising pressure means the breather path is restricted or more gas is entering the crankcase than it can vent. More on SPN 101.

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

Severity

HIGH — limit use, diagnose now

Many engines derate on high crankcase pressure and some shut down. Short, light running to a shop is usually OK if the oil level is right and oil isn't being pushed out.

Likely causes

  1. Plugged crankcase ventilation (breather) filter — the most common cause
  2. Pinched, plugged or frozen vent tube, separator drain or check valve
  3. Ice or moisture in the sensor port after cold starts below freezing
  4. Excessive blow-by from worn or broken rings
  5. Air compressor or turbo seals pressurising the crankcase
  6. Failed sensor or wiring

Checks & fixes (easiest first)

  1. Replace the crankcase breather filter if it is due or unknown
  2. Follow the vent path for kinks, sludge, a stuck check valve or ice
  3. Pull the sensor and inspect the port for water, ice or sludge; verify near-zero reading engine-off
  4. Isolate the air compressor and watch for a change in pressure
  5. Do a proper blow-by test before suspecting rings

Troubleshooting guides

FAQ

What does SPN 101 FMI 16 mean?

Engine Crankcase Pressure — 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 101 FMI 16 serious?

Many engines derate on high crankcase pressure and some shut down. Short, light running to a shop is usually OK if the oil level is right and oil isn't being pushed out.

What should I check first for SPN 101 FMI 16?

Replace the crankcase breather filter if it is due or unknown; Follow the vent path for kinks, sludge, a stuck check valve or ice; Pull the sensor and inspect the port for water, ice or sludge; verify near-zero reading engine-off.