The rear windshield of the SUV was damaged. Pieces of broken glass could be seen splattered on the road.
It has been alleged that an expelled party worker, Bullet Parimalam, was behind the attack.
Dinakaran broke away from the ruling AIADMK to form his own party and contest Chennai's RK Nagar by-election in December last year. He won comfortably from the seat previously held by J Jayalalithaa.