The 24-year-old’s loan runs until the end of June but there is scope to extend it until the end of the League of Ireland season in October.
He is under contract with PNE for another 12 months having signed a three-year deal in June 2017.
But he has not kicked a ball for the club since Boxing Day that year.
That game at Barnsley was one of only nine appearances in a Preston shirt.
His current stay at Cork is O’Connor’s third loan away from Deepdale in the last 18 months.
He has played for Fleetwood and Crewe, with Cork taking him back to Turners Cross in February.
It was Cork who North End signed o’Connor from, together with Sean Maguire.
Since his return to Cork, O’Connor has been playing in midfield.
Their interim manager John Cotter told the media in Ireland: “We all know what a good footballer he is and it was just a matter of having a bit of patience.
“Kevin has had an run in the team, his confidence is high and his fitness levels are getting better.
“He loves it here, we knew that before he went away.
“Kev is a great lad, great to have around the place and he’s been brilliant for us in the last few weeks.
“He’s shown that he can play in a few positions as well.
“We’d be delighted to keep him if that’s possible.”
The headline moment of O’Connor’s stay at Preston was winning one million euro on the Irish lottery in January 2018.
His signing from Cork was agreed in the closing stages of Simon Grayson’s reign. O’Connor was brought in as cover for Greg Cunningham but when Cunningham was injured early in the 2017/18 season, it was Josh Earl who went into the side.
His chance came when Earl was injured in November 2017 but Cunningham’s return saw him drop out.
If O’Connor’s loan at Cork is extended to the end of their season in the autumn, it would leave him in limbo for a while when it ends.
He would not be able to move again until the January transfer window.
A number of PNE players finished the season on loan with other clubs.
Of those, O’Connor, Chris Maxwell, Graham Burke and Connor Simpson have time left on their contracts.
Meanwhile, PNE defender Jack Armer has signed his first pro contract after graduating from the club’s academy.
Local lad Armer, 18, has penned a one-year deal with the option of a further 12 months.