Robot mower stops and shows E4 when trying to start the blades.
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn the main power switch OFF, remove the key (if fitted), and wait until all moving parts stop. Wear gloves before touching the blades.
- Inspect cutting disc: Turn the mower upside down on a soft surface. Check for accumulated grass, twine, or branches wrapped around the cutting disc and motor shaft. Remove all debris carefully.
- Check blade condition: Inspect the small pivoting blades on the disc. Replace any broken, heavily worn, or bent blades using Honda‑approved replacements and the correct screws.
- Spin test: Rotate the cutting disc by hand. It should turn freely without grinding or tight spots. If it is stiff or seized, the blade motor bearings may be damaged.
- Check for deck damage: Ensure the cutting disc is not rubbing against the mower deck or housing. If it is, inspect for bent mounting points or impact damage.
- Restart: Return the mower upright, power it ON, and start a manual mowing cycle to see if E4 clears.
If the disc still stalls or E4 reappears, the blade motor or its driver circuit on the main PCB may need replacement by a qualified technician.