Paulo Barreto put the visitors in front in the 25th minute with his second goal in as many games, but a second-half fightback looked like it was going to take Bologna into the top half of the table.
Panagiotis Kone scored first in the 65th minute with Tiberio Guarente putting the hosts in front in the 87th minute.
The game was not over, though, and Torino substitute Bianchi stole in to grab an equaliser with the last kick of the game.
Torino started brightly and Barreto confirmed his strong recent form to put them in front.
Mario Santana's shot was too hot for Gianluca Curci to handle and the ball looped up for Barreto to nod in from point blank range.
Bologna thought they had levelled just before half time when Kone chipped the ball into the back of the net over Jean-Francois Gillet, but the referee had already halted play for a foul by Alberto Gilardino.
There was similar controversy at the other end of the field moments later when Kamil Glik had a goal ruled out for another foul on a defender inside the penalty area.
Kone brought Bologna level midway through the second half, and there were no doubts about this goal as he headed in a sweeping cross from Domenico Morleo from six yards out.
Bologna went in search of a winner and they thought they had found it in the 87th minute when Guarente converted after Manolo Gabbiadini tucked Kone's cross back to him.
But Bianchi was to have the final say as he met Gyorgy Garics's low cross right in front of goal and lifted the ball into the roof of the net as the referee blew for full time.