Code 23
Onan
Low Oil Pressure Shutdown
Generator shuts down; Code 23 displayed indicating low oil pressure
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Low engine oil level, Faulty oil pressure switch or sensor, Clogged oil filter restricting flow, Worn oil pump or engine bearings causing low pressure
How to Fix / Troubleshooting
Safety first: Do not repeatedly restart a generator with a low oil pressure fault; severe engine damage can occur. Disable auto-start and allow engine to cool.
- Check oil level: Use the dipstick to verify oil level. Top up with the correct grade oil recommended by Onan. Do not overfill.
- Inspect for leaks: Look around the oil filter, drain plug, valve cover, and crank seals for fresh oil. Repair leaks and clean up spilled oil.
- Replace oil filter: If the unit is due for service, replace the oil filter with an Onan-approved filter and change the oil. A clogged filter can reduce pressure.
- Test oil pressure switch: Locate the oil pressure switch/sensor and inspect the connector. With a mechanical gauge (technician-level), verify actual oil pressure. If pressure is normal but Code 23 persists, replace the oil pressure switch/sensor.
- Engine wear: If actual oil pressure is low, internal engine wear or oil pump failure is likely. Do not run the unit; contact a qualified technician.
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Repair Difficulty
Hard
4/5
Required Part
Oil Pressure Switch
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