Only when in the car and stopped or you are personally carrying.
2923.12 Carrying concealed weapons.
(B)(1) If the person is stopped for a law enforcement purpose and is carrying a concealed handgun, fail to promptly inform any law enforcement officer who approaches the person after the person has been stopped that the person has been issued a concealed handgun license and that the person then is carrying a concealed handgun;
(C)(1) This section does not apply to any of the following: (c) A person's transportation or storage of a firearm, other than a firearm described in divisions (G) to (M) of section 2923.11 of the Revised Code, in a motor vehicle for any lawful purpose
if the firearm is not on the actor's person;2923.16 Improperly handling firearms in a motor vehicle.
(E) No person who has been issued a concealed handgun license, who is the driver or an occupant of a motor vehicle that is stopped as a result of a traffic stop or a stop for another law enforcement purpose or is the driver or an occupant of a commercial motor vehicle that is stopped by an employee of the motor carrier enforcement unit for the purposes defined in section 5503.34 of the Revised Code, and who is transporting or has a loaded handgun in the motor vehicle or commercial motor vehicle in any manner, shall do any of the following:
(1) Fail to promptly inform any law enforcement officer who approaches the vehicle while stopped that the person has been issued a concealed handgun license and that the person then possesses or has a loaded handgun in the motor vehicle;
(2) Fail to promptly inform the employee of the unit who approaches the vehicle while stopped that the person has been issued a concealed handgun license and that the person then possesses or has a loaded handgun in the commercial motor vehicle;
http://codes.ohio.gov/orc/2923