Any vehicle with an engine has a reserve of Power Points (abbreviated "pp.") The number of power points a vehicle has are based on its engine. A number of vehicular devices 'use up' power points to function. Power points are only regained when the vehicle refuels, recharges its batteries, etc.. Some engine types have a "recharge rate." This is the number of pp (per round) that the vehicle recharges, to a maximum of its normal amount of pp. Engine types with a recharge rate last, unless otherwise specified, essentially forever.
If a vehicle hits 0 pp (even if it can recharge) all electronic systems (i.e., basically everything) immediately shut down until the vehicle gets to 1 or more pp.