Jimenez shared the low round of the day with a 62 to move to 15-under-par 129. Anders Hansen also recorded a 62 to finish two shots further back in a group at 13-under-par 131, but the course record set a day before remained out of reach.
Fredrik Jacobson, who tied the European Tour's 18-hole record with a 60 on Thursday, managed only a 1-under 71 to join Hansen, K.J. Choi and Gary Orr in a tie for fifth.
Poulter tallied five birdies on the front nine at Golf Club Gut Larchenhof to make the turn at 12-under. He continued his fine play on the inward half with back-to-back birdies from the 12th and a birdie at the 15th.
The Englishman took over the top spot at the par-4 17th. Poulter knocked his second shot to six feet and ran home the putt to secure the 36-hole lead.
'I want to try and focus on what I have been doing over the past few weeks which is hitting good golf shots, shot after shot, and if I manage to do that, then the rest of the stuff will take care of itself,' said Poulter, who has two victories so far in 2003. 'But where I am at the moment, I am very, very happy.'
Jimenez collected 10 birdies and no bogeys to match his career best on the European Tour.
'I have played well here in the past and I like the place which helps a lot,' said Jimenez. 'I also feel very comfortable on the golf course and this week it has been in perfect condition, it was superb.'
Jacobson had a late tee time on Friday and despite the blistering opening round, he found himself trailing when he took to the first tee.
The Swede racked up two birdies over his first six holes and added a birdie at the eighth to tie Jimenez at minus-15. At the par-4 ninth, Jacobson landed his approach inside 12 feet and drained the putt to regain the outright lead.
Jacobson struggled with back-to-back bogeys starting at the 11th, but he managed to recover with a birdie at the 13th and another at the 15th.
At the par-3 16th, Jacobson's tee shot missed the green and almost bounced into the water. He chipped his second, but again his ball could not reach the putting surface and rolled back down the hill and into the drink.
Jacobson double-bogeyed the hole and closed with a bogey at the last to finish three shots back.
'When I won in Portugal in April, I was leading after the first round and then fell back a little bit and then came back to win,' said Jacobson, who has won twice on the European Tour this season. 'It is difficult to do it but I have done it many times before. I never give up, that is my motto.'
Miles Tunnicliff had a 63 of his own to join Carlos Rodiles in a tie for third at 14-under-par 130.
Paul Casey finished alone in ninth place at 12-under-par 132. Peter Hedblom and Jarrod Moseley were one shot further back at 11-under-par 133.
The 36-hole cut fell at 4-under-par 140. Among those missing the weekend are Padraig Harrington, Colin Montgomerie and European Ryder Cup captain Bernhard Langer.
'I am very disappointed,' said Langer, who is a four-time champion of this event. 'I came in here in good shape but I made too many bad strokes.'