A vehicular lock system used in combination with a battery has at least one latch settable in an unlocked position, a locked position permitting manual opening only by a key, and an antitheft position preventing manual opening even with the key. An electric servomotor is powered by the battery to displace the latch between at least the antitheft and locked positions. This servomotor is unable to move the latch between the positions when the battery power is below a predetermined minimum. An externally operable control unit is connected between the battery and the servomotor for feeding the battery power to the servomotor for displacing the latch at least between the antitheft and locked positions. A reference signal corresponding to the minimum battery power is compared to the battery power to displace the latch from the antitheft position to the locked position when the battery power falls below the predetermined minimum represented by the reference signal.