The Jets' best drive stalled when Mark Sanchez fumbled at the 49ers' 25-yard line while scrambling in the final two minutes of the half. It was the second fumble of the game for New York.
The 49ers took advantage of the turnover by quickly driving down the field for a 36-yard field goal by David Akers as time expired in the half.
San Francisco scored early in the second quarter, using backup quarterback Colin Kaepernick as a running threat. Kaepernick scored on a 7-yard run to give the 49ers the first lead of the game. The touchdown capped an eight-play, 68-yard drive.
The 49ers had a chance to add to the lead on their next drive, but Akers missed a 50-yard field goal.
The San Francisco offense accumulated 210 yards of offense in the first half while New York only managed 83 yards.
Both teams came into the Week 4 matchup at 2-1, but New York enters after winning in overtime last week while San Francisco is trying to bounce back from their first loss of the season.