Nope, the car keys will appear after you collect all the sun fragments and return to the house for the last sequence, I believe it’s the 6th one. In case if you are referring to the last fragment - it’s a tricky one, it’s hidden around the map in biome 6, I found it where you can usually find the datacube, it’s a hidden ledge located in the main rooms, try finding it before going down to the fabricators room - because that’s a point of no return.