I don't have the recipe for a foot crank but it seems to me like I should

[Valase]

Nothing changed since when your question was answered almost one year ago:

I can’t remember how to add pedals to a vehicle

As Junknown pointed out, they are no longer craftable, and as PALU suspected, you probably took off a broken (XX) pedal which only returns part(s)… As for installing them in a vehicle, they are called foot pedals, are located in the Internal category, require a foot crank, mechanics skill of 0, a tool with bolt turning of 2 and are installed onto any kind of frame (information accurate as of build version 0.E-10998). Also, there can only be one installed pedals per vehicle.