Kimi Raikkonen's Ferrari had to stay in the pits for over three hours on Tuesday because of a problem with the Kinetic Energy Recovery System (KERS) during testing in Bahrain.
KERS recovers and stores as electrical power the energy generated and otherwise lost when a car brakes.
"Kimi Raikkonen's last test day at Sakhir wasn't born under a lucky star. Just after 11.30 am the car started to have a problem with the KERS' cooling circuit and the Finnish driver had to come to the box," a Ferrari statement said.
"The stop to repair the KERS took more than three hours. Nevertheless there was one positive aspect, as the team was able to experiment with an emergency in case of a KERS failure."
KERS is not mandatory and teams have reserved judgment on whether they will be in a position to use it at the season-opening race in Australia on March 29. Testing is prohibited during the season.
The Bahrain tests, which have also included BMW Sauber and Toyota, were blown out by a sandstorm for two days last week.