With less than two minutes to play, the Titans had slashed USC's once-comfortable lead to only two points.
But the Trojans' defense stiffened and a dunk by USC guard Julian Jacobs with four seconds left sealed a victory that lifted USC's record to 3-3. Fullerton dropped to 1-3.
"We held them to 32%," Enfield said of the Titans' 18-for-56 shooting.
USC forwards Darion Clark and Nikola Jovanovic combined for 25 rebounds, 14 by Clark.
"They really helped us inside," Enfield said.
Jovanovic also led the Trojans in scoring with 13 points.
Even so, Enfield said, "We still missed a lot of easy shots. At some point you've got to step up and make shots."
USC opened the second half by quickly stretching its lead to 12 points, 33-21, on Katin Reinhardt's second three-point field goal of the night and a short jump shot by forward Strahinja Gavrilovic.
As the Lakers' Nick Young, a former Trojan, watched and ate popcorn from a courtside seat, USC soon built its lead to 40-26 with 12 minutes remaining.
But the Titans steadily chipped away, in large part because guard Lanerryl Johnson began converting one three-point jump shot after another.
"He shot the lights out," Enfield said.
Johnson converted five of seven three-point attempts and scored a game-high 21 points. Moses Morgan added 10 points for the Titans.
The Trojans led at halftime, 24-19, thanks to a team-wide effort as Clark, Jovanovic and Reinhardt each scored six points and Jacobs added four.
Clark led the way. The Georgia native converted all three of his field-goal attempts and pulled down a team-high eight rebounds in the half.
Guard Jordan McLaughlin, who entered the game as USC's leading scorer with an average of 13 points per game, failed to score in the first half and finished with four points for the game.
Both teams endured an extended scoreless streak in the first half.
After Clark's layup gave USC an 18-17 lead with 6:39 left in the half, neither team scored for nearly four minutes, until Jovanovic finally made a layup with 2:43 remaining.
The Trojans shot 36.7% from the field in the first half, compared with 30.8% for the Titans.