The comedian first made the surprise announcement alongside co-star Sian Gibson live during BBC Children in Need last year.
Now the BBC has confirmed the final ever shows will air in May. The first aired last week at 10PM on Monday, May 7 at 10PM while the second will air at 10PM on Monday, May 28.
The first special episode was called Car Share: Unscripted and followed John and Kayleigh home on their daily commute only the entire episode will be completely improvised.
The entire show followed them home on their daily commute and features what was filmed whilst driving around with no script.
Peter said: "I think it’s always good to try and do something original and I couldn’t think of any other narrative comedies that have ever made a fully improvised episode.
"As Sian and myself often ad lib when filming we thought we’d give it a go for an entire episode."
The Unscripted special will be followed by one final episode to be broadcast later (on May 28), revealing just what happens next to John and Kayleigh.
Car Share viewers were left in dismay at the end of the second series when Kayleigh stepped out of John’s car and his life forever.
Fans even set up online petition demanding a conclusion to the series which gathered over 100,000 signatures.
In the run up to the last episode, a repeat of Series 2 will air on Mondays at 9PM on BBC One.
Peter Kay said in 2017: “We were completely overwhelmed by the response and even though we've no plans to write a third series we knew we couldn't end the story there.”
Peter said last year: "We were always very fond of ad libbing around the script when we were filming the series so we decided to see what would happen if we took the script away and just relied on just our chemistry alone, reacting to whatever came on the radio."
Charlotte Moore, Director of BBC Content commented: "I know it will be music to the ears of millions of fans of Peter Kay's joyous award winning comedy to hear that Kayleigh and John will be coming back for one last time with a very special finale episode in 2018."
Shane Allen, Controller Comedy Commissioning added: "Car Share has been the hit comedy of 2017 with audiences of over 11 million.
"This new finale is going to be the TV comedy equivalent of The Space Landing, ‘Who Shot J.R.?’ or The Olympics Opening Ceremony depending on how old you are”