The Yaounde victory sealed first place in Group I for the ‘Indomitable Lions’, who finished four points clear of their opponents.
Chedjou, who recently signed a four-year contract with Turkish club Galatasaray, netted three minutes before half-time.
Cameroon suffered a blow on the hour mark when new Chelsea signing Samuel Eto’o limped off to be replaced by Jacques Zoua.
A draw would have been enough for six-time World Cup qualifiers Cameroon while Libya needed maximum points to keep alive their dreams of a first appearance.
Libya set the pace for much of a six-round mini-league that began in mid-2012, but Togo did them no favours last June.
The Togolese fielded a suspended iplayer in a 2-0 win over Cameroon, who were awarded a 3-0 victory and three points.
Instead of facing Libya in second place two points adrift, the ‘Lions’ had a one-point lead and home advantage at Stade Ahmadou Ahidjo.
Cameroon were the last nation to reach the play-offs, joining Algeria, Burkina Faso, Cape Verde, Egypt, Ethiopia, Ghana, Ivory Coast, Nigeria and Senegal.
A seeded draw, based on the latest FIFA rankings, will be made on September 16 in Cairo.
And the winners of five two-leg ties scheduled for October and November, go to Brazil.
Togo finally had cause to celebrate when a stoppage-time goal from Backer Aloenouvo delivered a 2-1 home win over the Democratic Republic of Congo.
Lalawele Atakora put the Togolese ahead during the first half in Lome and Saoule Ebunga equalised nine minutes from time.
Benin completed their Group H campaign with a 2-0 victory over bottom side Rwnada in Porto Novo through goals from Mickael Pote and Bello Babatuinde.
Kenya ended a five-match win drought in the qualifying competition by edging visiting Namibia 1-0 in Nairobi.
Defender David Owino scored after five minutes to give the ‘Harambee Stars’ maximum points from their final mini-league fixture.
The result meant a change of positions in the final standings with Kenya climbing to third and Namibia dropping to last place.
African champions Nigeria won Group F on Saturday by defeating Malawi 2-0 in Calabar as they look to qualify for their second straight World Cup after going out in the first round in South Africa.
Zimbabwe and Mozambique drew 1-1 in Harare, leaving the southern Africa neighbours winless after six Group G matches each.
Captain Masimba Mambare put the home side ahead just before half-time and substitute Maninho levelled on the hour mark.
Egypt were runaway winners of the group and complete their schedule Tuesday at home to second-placed Guinea in El-Gouna. Mozambique finished third and Zimbabwe last.