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During the Seeds of the Past main quest, Aloy will scour the Elm Testing Station with her newest companion, Alva. Together, the two brains have to solve the puzzles inside to get the information they are looking for. One part in particular can be particularly elusive, the service key.
Related: All outfit locations in Horizon Forbidden West
Where the maintenance bypass key hides
After entering the greenhouse through an opening, players have several levels of this inner chamber to explore. First go to the bottom floor and then to the far right corner where there is a battery storage container. Pull this out of the wall and check the space behind it. This is where the maintenance bypass key is located.
For more Horizon Forbidden West content, see All Black Box Locations in Horizon Forbidden West in the Pro Game Guides.
https://progameguides.com/horizon-forbidden-west/where-to-find-the-maintenance-key-in-test-station-elm-in-horizon-forbidden-west/ Where can I find the maintenance key in the Elm test station in Horizon Forbidden West?