SPN 22 — Engine Extended Crankcase Blow-by Pressure
System: Crankcase ventilation
A blow-by pressure or flow reading taken in the crankcase ventilation path on engines that monitor it. It is used to spot excessive blow-by past the rings or a restricted breather.
Can I keep running it?
HIGH — limit use, diagnose now
High blow-by readings usually come with a derate. Check the breather system first, then test the engine; continued hard running can push out seals and worsen internal damage.
Likely causes
- Plugged crankcase breather filter or oil separator
- Restricted, kinked or frozen vent/draft tube
- Worn or broken piston rings, or a damaged piston
- Air compressor or turbo leaking pressure into the crankcase
- Sensor, sensor port or wiring fault
Checks & fixes (easiest first)
- Check oil level and when the breather filter was last replaced
- Inspect the vent hoses and draft tube for kinks, sludge and ice
- Verify the sensor reads near zero with the engine off and the port is clean
- Perform the OEM blow-by test with a manometer at the specified speed and load
Common FMIs with SPN 22
- SPN 22 FMI 0Value too high (most severe)
- SPN 22 FMI 2Data erratic, intermittent, or incorrect
- SPN 22 FMI 3Voltage above normal or shorted high
- SPN 22 FMI 4Voltage below normal or shorted low
- SPN 22 FMI 16Value too high (moderately severe)
Related codes
Troubleshooting guides
FAQ
What does SPN 22 mean?
SPN 22 is Engine Extended Crankcase Blow-by Pressure. A blow-by pressure or flow reading taken in the crankcase ventilation path on engines that monitor it. It is used to spot excessive blow-by past the rings or a restricted breather.
Can I keep running with SPN 22?
High blow-by readings usually come with a derate. Check the breather system first, then test the engine; continued hard running can push out seals and worsen internal damage.
What causes SPN 22?
Plugged crankcase breather filter or oil separator; Restricted, kinked or frozen vent/draft tube; Worn or broken piston rings, or a damaged piston; Air compressor or turbo leaking pressure into the crankcase; Sensor, sensor port or wiring fault.