Mercedes called a halt to their first day of Formula One testing today after Nico Rosberg stopped on track with flames flaring briefly around the back of his car.
The team blamed an electrical fault.
"After identifying the cause of the problem, we will not be running again today whilst parts are modified ready for tomorrow," Mercedes said on their Twitter feed.
"The part which requires modification is the wiring loom where the electrical fault originated this morning."
Rosberg completed 14 laps at the Jerez circuit in the F1 W04 car that he and new team mate Lewis Hamilton unveiled to the world on Monday.
Hamilton, the 2008 world champion who has moved from McLaren, is due to have his first proper run in the car tomorrow.
Mercedes were fifth overall last season and the Briton, who replaces Germany's seven-times world champion Michael Schumacher, could have a hard road ahead of him before the regulations change in 2014.
The 2013 season starts with the Australia Grand Prix on March 17.