Lalime, making his first NHL start this season after undergoing back surgery for a herniated disc in September, stymied the Canucks with 34-save performance to earn his 34th career shutout.
Aucoin's go-ahead goal that helped end his club's winless streak against the Canucks at six games was a strange one and came unassisted 36 minutes 14 seconds into the game.
His shot hit the stick of Vancouver defenceman Kevin Bieksa and bounced into the net over goalie Roberto Luongo, who was flat on his back.
Luongo had been flopping around his crease trying to corral a loose puck that was eventually cleared by defenceman Willie Mitchell, but it went to Aucoin at the Canuck blue-line.
Radim Vrbata and Martin Havlat clinched the victory with empty-net tallies in the final minute.
Chicago (21-26-7), which last beat Vancouver on March 19, 2004, also denied Vancouver first place in the Northwest Division.
The Canucks (30-21-4) remained a point behind the idle Calgary Flames who have two games in hand.
Chicago defeated Calgary in a shootout on Tuesday and have won four of their last five games, but need to make up ground in a hurry if they are to contend for a playoff spot.
Lalime was tested with 12 shots in the scoreless, sluggish first period but Luongo had the tougher saves.
The Vancouver netminder got a glove on a Tuomo Ruutu shot labelled for the top corner, smothered a Tony Salmelainen drive from close in and blocked a quick shot from Denis Arkhipov.
Lalime, who had a bouncing puck hit his shoulder earlier in the second period, preserved the one-goal edge heading into the third by getting in front of Daniel Sedin's power-play deflection.
The Blackhawks were outshot 27-18 after 40 minutes but Luongo needed his quick glove again to deny Peter Bondra and another shot heading for the top corner.
NOTES: Alexander Edler returned to the Canuck blue-line, replacing Lukas Krajicek who was knocked out of Tuesday's win over Edmonton by Zack Stortini's heavy hit ... Chicago called up forwards Craig MacDonald and Pierre Parenteau from AHL Norfolk and placed Michael Holmqvist (back) and Jeff Hamilton (shoulder) on injured reserve ... Canuck Kevin Bieksa pummelled Karl Stewart of the Blackhawks in a third-period scrap ... Chicago has two games left on a season-high seven-game road trip before facing the Canucks again at the United Center on Feb. 16.