Hotwire is a special skill available to William J. Blazkowicz in the Fergus timeline of Wolfenstein: The New Order. The skill is acquired shortly after the beginning of the timeline, when the player has to escape the incinerator room of Deathshead's Compound.
Hotwiring allows the player to undo electronic locks and access areas that are unique to the Fergus timeline, or take specific shortcuts in certain levels. In the Eisenwald Prison mission, hotwiring a panel in the prison control room can be used to disable a number of automated sentry guns in the level.
Health Upgrades are usually located in areas accessed via hotwiring. Several levels contain easily recognizeable strongboxes with electronic locks, which contain some ammo and a Health Upgrade.
Once they find an electronic lock, players first need to interact with it, in order to peel off its protective cover. Once this is done, the two wires have to be connected long enough for the three green lights to activate. Once all three indicators are lit, the door is unlocked.
Lockpicking - the other timeline's equivalent of hotwiring.