Safety issues are the focus of attention in F1 after five drivers suffered tyre blow-outs at last Sunday's British Grand Prix and the risk of fire in the pitlane is another significant danger.
"At 08.30 this morning the Williams F1 team suffered a KERS failure on Pastor Maldonado's car," a team statement said, referring to the kinetic energy recovery system.
"The car was in the garage at the time. The resulting smoke was contained quickly and efficiently by the team and circuit fire marshals. No personnel were injured."
Maldonado later took to the track in final practice before qualifying and his car looked to have suffered no ill effects as he posted competitive times, although he did almost lose the back end on a corner.
"Our boys really do do an amazing job as Pastor is ready to go for the start of free practice," Williams tweeted, thanking Caterham, Force India and Marussia for their help in dealing with the issue.
Williams suffered a fire in their garage at last year's Spanish Grand Prix where seven people were taken to hospital and 31 needed medical attention. It came after their first race win in eight years through Venezuelan driver Maldonado.
Last year's win in Spain turned out to be a false dawn. Maldonado and Finnish rookie team mate Valtteri Bottas have yet to score a point in eight races this season for the British team who were last champions in 1997.