McLaren's David Coulthard suffered an engine problem in the warm-up for today's Spanish Formula One Grand Prix.
The Scot, joint championship leader with Ferrari's Michael Schumacher, pulled over to the pit wall near the end of the straight after his car spewed out smoke as the session drew to a close.
A Mercedes spokesman said however that the engine was not damaged and would not need changing for the race.
"It was a hydraulics pressure problem. The emergency system cut off the engine immediately," he said.
Ferrari's Brazilian Rubens Barrichello was fastest in the session, with several drivers switching from race car to spare as they fine-tuned the set-up.
Barrichello's time was one minute 20.680 seconds, ahead of McLaren's Mika Hakkinen in 1:20.901. Coulthard, who starts on the second row behind Hakkinen and Schumacher, was third fastest in 1:21.148.
Schumacher was fourth in 1:21.211.
The race starts at 1200 GMT. Hakkinen, twice world champion, has won at the Circuit de Catalunya for the last three years.