De Jong scored his 14th league goal of the season in the 75th minute to lift PSV to 38 points, level with Ajax who have a better goal difference and host Graafschap on Sunday.
Uruguayan striker Gaston Pereiro scored twice in the opening 15 minutes as PSV got off to a flying start.
PEC were level by halftime, however, as Bram van Polen converted a penalty in the 40th minute and Lars Veldwijk equalised three minutes later.
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De Jong grabbed the winner when he headed home Maxime Lestienne's cross.
Heracles Almelo defender Gino Bosz converted a last-minute freekick as they beat Groningen 2-1 to move up to fourth on 30 points.
Bryan Linssen handed Groningen the lead but it lasted only minutes before Paul Gladon equalised.
AZ Alkmaar's Jeffrey Gouweleeuw netted a stoppage time penalty in a 2-2 home draw with Utrecht.
Mattias Johansson gave AZ a 27th-minute lead and the home side thought they had doubled their advantage 10 minutes from time, but Robert Muhren's effort was ruled out by the referee, although it was not immediately clear why.
Utrecht then snatched two goals in three minutes from Ruud Boymans, making his return after a year out with injury, and Sebastien Haller, before they conceded a late penalty, which Gouweleeuw converted.
Dutch international defender Ron Vlaar made his AZ debut having returned to the Netherlands after more than three years at Premier League Aston Villa.
(Reporting by Mark Gleeson; Editing by Toby Davis)
