Pietersen had come under fire during the opening two Tests of the Ashes after getting out to a series of rash shots.
His second innings knock of 53 in Adelaide was a more disciplined display, and he took the same mantra into the third Ashes Test at the WACA, where he faced 58 balls and spent 95 minutes at the crease as he crawled to 19.
During that time, he became the fifth Englishman to reach 8000 Test runs.
But under Perth's searing heat, Pietersen couldn't hold his composure any longer, producing a lazy swat at a rising Siddle delivery.
Mitchell Johnson took a superb stumbling catch at mid-on to send Pietersen packing.
It was the 10th time in Test cricket Pietersen had fallen victim to vegan warrior Siddle.
But more importantly, Pietersen's dismissal left England precariously placed at 4-180 at stumps on day two in reply to Australia's 385.
With England trailing 2-0 in the series, they desperately needed Pietersen to fire in Perth.
He still has one more chance to do that, but he'll have to overcome his rashness and a hungry Siddle.
Australia's bowling coach Craig McDermott said Siddle had executed his plans towards Pietersen perfectly.
"He just bowls very tight lines to Pietersen, and had good patience," McDermott said.
"He was four off 40 balls and he was digging himself a fair hole from my perspective.
"And then he started playing a shot a ball.
"Sids has just tied him down time and time again and then the release valve comes, and Sids cracks him open.
"That's great for us and we hope that continues."
THE BOWLERS WHO TERRORISE ENGLAND'S KEVIN PIETERSEN:
* Peter Siddle (Australia) 10 times in 15 matches
* Brett Lee (Australia) 6 times in 10 matches
* Muttiah Muralitharan (Sri Lanka) 6 times in 6 matches
* Morne Morkel (South Africa) 5 times in 10 matches
* Shane Warne (Australia) 5 times in 10 matches
* Glenn McGrath (Australia) 5 times in 8 matches
* Shantha Sreesanth (India) 5 times in 8 matches
* Saeed Ajmal (Pakistan) 5 times in 6 matches.