Three ahead overnight, 46 year old Jiménez added birdies on the first and sixth to stand 19 under par.
Ryder Cup team-mate Edoardo Molinari - last week's winner at Gleneagles - had two birdies and a bogey over the same stretch, while his 17 year old fellow Italian Matteo Manassero was three shots further back in third.
Victory would make Jiménez the first European since Johan Edfors in 2006 to win three European Tour events in the same season.
Sunday’s attendance of 13,900 ensured a new record of 52,700 spectators had enjoyed the week’s action at Crans-sur-Sierre, beating the previous best of 52,500 in 2006.
Jiménez stretched his advantage to six with further birdies on the seventh and ninth.
Molinari parred them and was caught in second place when Manassero, on course to secure a European Tour card for next season in just six starts as a professional, finished the outward half with a hat-trick of birdies.
Molinari cut the gap to five with a birdie at the 12th and another on the long 14th put him only three back as Jiménez, bunkered off the tee and over the green for three, ran up a bogey six.
It was suddenly game on again when Molinari hit a brilliant six iron approach to two feet on the 516 yard 15th and holed for eagle.
Jiménez did not even birdie and so led by just one with three to play.
Molinari, of course, had been two behind at the same point last Sunday and birdied them all.