The Sky Blues pulled away from the relegation zone as Colchester and Scunthorpe headed for spending next season in League One after defeats.
Bottom side Colchester lost 4-3 at Scunthorpe after leading twice whilst Scunthorpe were beaten 1-0 at Leicester thanks to a Lee Hendrie goal.
Sheffield Wednesday remain third bottom. They trailed 1-0 to league leaders Stoke City but a goal by Songo'o in the 82nd minute earned the Owls a draw.
One of the Owls two games in hand is against the Sky Blues on Tuesday night and Wednesday have 45 points, one behind Southampton who lost 1-0 at Wembley bound Cardiff City.
Talking of Wembley bound, fifth bottom are Barnsley beaten 2-1 at Burnley.
Bristol City top the Championship table after a 2-1 home win against Norwich City. Former Sky Blue Dele Adebola put the Robins ahead with Darren Huckerby scoring a late consolation goal for the Canaries.
Third placed Hull City put in another excellent performance to beat Watford 3-0 at the KC Stadium.
Elsewhere, home form specialists Preston beat Sheffield United 3-1, Wolves won 3-2 at Charlton and the games at Ipswich and Crystal Palace ended in 0-0 draws.
Those clubs in the Championships next season will have a trip to Derby County. The Rams were relegated after a 2-2 draw with Fulham at Pride Park. Their plight was not helped by a Dean Leacock own goal.
Coventry City target Gary McSheffrey scored with a penalty for Birmingham City in a 3-1 win against Manchester City.
Colin Hawkins played the whole game for Chesterfield in a 3-0 win at Dagenham & Redbridge but Wayne Andrews lasted only seventeen minutes of his Bristol Rovers debut at Yeovil when he carried off following a crunching tackle by Terry Skiverton.