Fox-Pitt, who won Olympic team eventing silver at London 2012 and Athens 2004 and bronze at Beijing 2008, scored 36.60 aboard Chilli Morning to slot into second place individually behind Michael Jung in Malmo.
That helped Britain remain third overall with Izzy Taylor placing ninth and Kristina Cook 12th after the second day of the dressage with Lucy Wiegersma now 17th and Pippa Funnell 25th.
All five will go in the cross-country next before the jumping on Sunday with Fox-Pitt missing just one flying change during what was an otherwise impressive performance with Chilli Morning in the dressage.
"The flying change was annoying because that's one of his best movements," said William. "Chilli is very handsome and he knows it.
"He's quite a challenge because he can be boisterous and yet you need to be gentle with him. You have to humour him."
© Sportsbeat 2013