Wood left his boyhood team in November for the Ricoh Arena and looked to be heading for defeat with the Sky Blues after a superb 67th minute strike from Luke Varney put them 1-0 down.
But he rose to meet a long Sammy Clingan ball 11 minutes later to level the tie.
There were plenty of chances in the early stages of the game and the visitors could have been ahead in the fifth minute when a sliced Marcus Hall clearance bobbled towards Darren Potter, who fired the ball towards the bottom corner only for keeper Keiren Westwood to push wide.
At the other end, Wood headed a Clingan corner towards goal but it was cleared off the line by Potter.
Wednesday's Eddie Nolan was next to go close when he beat Hall on the edge of the area and shot towards goal, but Westwood managed to palm the ball away from goal.
Chris Coleman responded his side's lacklustre first half by making three half-time substitutions and he got the positive reaction he needed.
Within minutes, James McPake came within inches of a goal when his header from a Clingan corner brushed the bar and substitute Clinton Morrison converted a Freddie Sears pass only for it to be flagged offside.
But Wednesday worked their way back into the game and, after Leon Clarke saw a 60th minute header tipped onto the post by Westwood, Varney scored the crucial opener.
The forward beat David Bell twice as he drifted into the area from the left-hand side and then coolly slotted the ball home from a tight angle for his ninth goal of the season.
Wednesday seemed to be on the verge of pulling clear of the drop-zone but Coventry piled forward and when Clingan launched a long ball towards Wood, Owls keeper Lee Grant came to meet it on the edge of the box but was too late leaving Wood to nod home.
The Coventry players rushed to Wood but he refused to celebrate and trotted back to his own half silently.