With Monaco winning on Tuesday, Auxerre coach Guy Roux knew his side had to claim three points at struggling Sedan.
They fell behind early in the game, but second-half strikes from Djibril Cisse and Yann Lachuer earned them a vital three points.
Pius N`Diefi opened the scoring for Sedan, beating his marker before slamming a shot past Fabien Cool on three minutes.
Sedan belied their league position and dominated the opening 45 minutes, but failed to turn the pressure into a second goal.
Djibril Cisse attempted to spark life into Auxerre, and went close minutes into the second-half.
The French international eventually found his range and levelled the scores on 62 minutes.
Yann Lachuer was the architect, as he drew keeper Patrick Regnault before slipping the ball to Cisse and he rolled his shot into an empty net.
The game then flowed from end to end, with Auxerre chasing points for the title and Sedan for survival.
Sedan sub Stephane Noro thought he had stolen the points late in the game but he was denied by a superb save from Cool.
Noro was made to rue his miss, as Auxerre skipper Lachuer headed home a Khalilou Fadiga corner on 87 minutes to snatch victory.
Auxerre are now within two points of Monaco and have a game in hand, while Sedan are still deep in trouble near the foot of the table.
Marseille moved level on points with Monaco thanks to a professional victory over Le Havre.
Le Havre are scrapping for survival, but were made to look distinctly ordinary by Alain Perrin`s l`OM.
Russian ace Dmitry Sychev opened the scoring on 16 minutes as he beat two defenders before netting.
Belgian defender Daniel van Buyten has a real eye for goal and he netted the crucial second on 53 minutes from a Frank Leboeuf corner.
Nice`s title challenge suffered a jolt, as they were beaten 1-0 at struggling Troyes.
Rafik Saifi`s strike on three minutes was enough to give them three points but it was not enough to lift them off the foot of the table, as Montpellier won 2-1 at home to Strasbourg.
Paris Saint Germain`s recent good run ended at Bastia, as the Corsican side ran out 1-0 winners thanks to Florian Maurice`s first-half goal.
The game descended into chaos late in the game, as PSG duo Ronaldinho and Parralo Cristobal both saw red.
Gregory Pujol`s late goal was enough to give Nantes a 1-0 home win over Rennes.
The most exciting game of the evening was at Lens, as the home side were pegged back by Bordeaux as the game ended 3-3.
John Utaka, Daniel Moreira and Antoine Sibierski thought they had given Lens the points, but a brace of goals by Pauleta and a strike by Kodjo Afanou grabbed a point for Les Girondins.
To view a match summary, click on the link below
Bastia v Paris Saint Germain
Lens v Bordeaux
Marseille v Le Havre
Montpellier v Strasbourg
Nantes v Rennes
Sedan v Auxerre
Troyes v Nice
