A vehicular control system includes a smart key carried by a user and operated by an embedded battery and a verification ECU mounted in a vehicle. A wireless communication is made between the smart key and the verification ECU. The smart key performs periodically a switchover of a detection sensitivity for detecting a transmission electric wave transmitted from the verification ECU between a normal sensitivity and a high sensitivity. The high sensitivity has a detection area of the transmission electric wave greater than a detection area of the normal sensitivity. The constant use of the high sensitivity is unnecessary to detect the transmission electric wave. This enables a reduction of the consumed electric current of the battery for detecting the transmission electric wave with the high sensitivity.