The KERS unit aboard championship leader and Sepang winner Sebastian Vettel's RB7 was working on Sunday, Red Bull confirmed.

The German was told en route to back-to-back victory in Malaysia that he should not use the energy-recovery system, after teammate Mark Webber's unit failed.

"In the last laps Sebastian didn't use it any more," revealed team consultant Helmut Marko to German broadcaster Sky. "It was ready if he had needed it.

"We were just careful as we were racing McLaren," added the Austrian.

After electing to remove the technology from the RB7 cars in Australia, Malaysia was the first time Red Bull had used KERS in a grand prix.

Marko said: "We could see from the laptimes that KERS was not necessary for him (Vettel). We were quick enough without it."

Webber's KERS system failed not only in qualifying but also in Sunday's race, so team boss Christian Horner said Vettel was told not to use his late in the race "because we didn't want to risk" more problems.

Vettel won the race from McLaren's Jenson Button, after the German on Saturday secured pole by just a tenth of a second from Button's teammate Lewis Hamilton.

"We went about the grand prix in a different way, focusing more on the race and less on qualifying. China will be another challenge because it will be much cooler," said Horner.

Added Marko: "Our enemies will not sleep -- especially McLaren."