San Diego's Nick Novak made a 39-yard field goal with 54 seconds left in the half to extend the lead to 13-0, but the Chargers left too much time on the clock and Pittsburgh marched down the field to set up Suisham's field goal.
In his return from injury, Ben Roethlisberger's performance has been up and down. The veteran quarterback only completed 9-of-20 passing attempts for 105 yards in the first half, but he moved well while he evaded pressure and helped the Steelers move down the field for their only score just before halftime.
Philip Rivers hit Danario Alexander for a 39-yard touchdown down the left sideline to give San Diego a 10-0 lead after the Chargers got on the board first with a 51-yard field goal by Novak in the first quarter.
Rivers completed 10-of-25 passes for 114 yards and the lone touchdown.
San Diego will receive the ball to begin the second half.
The game is being broadcast on CBS.