Hello Junk. Thank you for your feedback. We are sorry to hear about the issues you are experiencing with your 21″ 40V Lawn Mower. What you are describing as the lawn mower running for a few seconds and then shutting off is not typical performance and usually indicates one of the following:
Battery/connection issue: Ensure the battery is fully charged and seated firmly in the mower. Check that the contacts on both the battery and mower are clean and free of debris.
Safety/engagement switch: The lawn mowers require the bail lever to be held properly, and all safety interlocks engaged. If a sensor is not detecting the lever or deck cover properly, it can shut the motor off.
Motor load cutoff: If the blade is blocked or the mower is under heavy load right at start, the motor may shut off quickly to protect the system. Make sure the deck is clear and the blade spins freely by hand (with the battery removed).
Fault code or component fault: Some units will shut down immediately if a component (controller, motor, sensor) is malfunctioning.
Before assuming a defective unit, try these troubleshooting steps:
Fully charge the battery and reseat it.
Verifying all safety levers are properly engaged.
Remove the battery and check for debris in the contacts.
With the battery out, confirm that the blade can spin freely and that there are no obstructions under the deck.
If the mower still shuts off after these checks, it may require service or a replacement part especially if it happens with a good battery and no load. Please reach out to our Customer Success team with your serial number and purchase details so we can assist you further. We want to ensure you get reliable performance from your lawn mower.
They can be reached either using the online chat function, on Greenworks Tools page, accessible by clicking “Chat Now” in the bottom corner of your screen, Chat with a Live Agent or by calling 1-888-909-6757.

Hello REVL. Thank you for sharing your feedback. We are sorry to hear about the issues you have experienced and that your interactions with our customer support has not met your expectations. We understand how frustrating this must be. It looks like our Product Experience team has already shared their findings with you. We encourage you to try the suggestions they provided, and if the issue persists or worsens, please reach out again so we can work with you to find a solution. Greenworks experts can help via: Online chat: Click “Chat with an Expert” on the Greenworks Tools page. Phone: 1‑888‑909‑6757 (M–F 9 AM–7 PM EST, Sat–Sun 9 AM–5 PM EST). Please have your unit, battery, charger, model, and serial number ready for quick troubleshooting.