Display shows E4 and the mower stops with the cutting disc not turning.
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: Switch the main switch to OFF and remove the mower from the lawn. Wait until all moving parts have completely stopped. Wear cut-resistant gloves.
- Inspect underside: Turn the mower on its side according to the manual (usually with the control panel facing up). Check for packed grass, twine, or branches jammed around the cutting disc and motor shaft.
- Clear obstructions: Carefully remove all debris using a brush or wooden tool. Do not use your bare hands near the blades.
- Check disc rotation: Gently rotate the cutting disc by hand. It should turn freely without grinding or tight spots. If it is stiff or wobbly, the disc or motor bearing may be damaged.
- Inspect blades: Ensure the pivoting blades are free to swing and not bent into the disc. Replace damaged blades with genuine Stihl iMOW blades and screws.
- Adjust mowing height: If the grass is very tall, raise the cutting height using the height adjustment knob and mow in stages, lowering the height gradually over several days.
If the disc still binds or the E4 error returns immediately, the mowing motor may be failing and should be tested and replaced by a Stihl service technician.