Although Sebastian Vettel says it was a "small failure" that sidelined him in practice, he concedes it will have "big consequences" for his weekend.
Vettel's latest title defence has not gone according to plan as the German and his Red Bull team have been blighted by various reliability issues and a lack of pace.
As such he arrived at the Circuit de Barcelona-Catalunya for this weekend's grand prix with a new chassis and renewed hope.
It came to naught on Friday.
Just four laps into his running the reigning World Champion's RB10 broke down at Turn 5.
Red Bull confirmed that it was an "electrical problem" that "damaged the wiring loom" forcing the car to stop out track.
It also meant the 26-year-old could not contest the afternoon session, limiting him to just four laps for the day.
"We had a simple failure in one of the looms this morning, which caused a short and meant the car stopped," Vettel explained.
"We had to change the chassis loom, which is a big job so I wasn't able to go out this afternoon.
"It's a small failure, but a big consequence; there was nothing new on that part of the car, it was something new that happened in that area.
"Luckily it happened today (rather than tomorrow), but unfortunately we lost the chance to prepare for Sunday with two cars, so I have to rely on what Daniel did today and get into the rhythm straight away tomorrow."
Daniel Ricciardo finished the day third quickest, 0.985s behind the pace-setting Lewis Hamilton.
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