Safety first: Switch OFF the mower and disconnect the charging station. Wear gloves.

Inspect wheels: Lift the mower and check both rear drive wheels (and front caster if fitted). Remove wrapped grass, twine, or roots from around the axles and inside the wheel treads.
Check wheel rotation: Manually rotate each drive wheel. They should turn with some gearbox resistance but without locking or grinding. A wheel that is locked or very rough indicates gearbox damage.
Clean underbody: Remove built‑up mud and grass from the underside that may be rubbing on the wheels.
Check drive motor connectors: Open the housing and locate the left and right drive motors. Inspect the connectors and wiring harness to the main PCB for damage or loose plugs. Reseat connectors.
Test individually: If your Parkside model allows, run a wheel test from the service menu (see manual). If one side fails, that drive motor/gearbox assembly likely needs replacement.

When to replace: Persistent E4 on one side after clearing jams usually means a failed drive motor/gearbox.

Robot mower displays E4 and stops; wheels may twitch but mower does not move.

Possible Causes