Toro Rosso have suffered their first major setback of winter testing after managing just one lap in the afternoon session on day five in Barcelona.
The Red Bull junior team looked poised to rack up another century of laps to take the Honda engine past its 2017 testing total of 425 laps. But, after Gasly posted 53 laps in the morning, he would add just one more in the afternoon.
Rumours of a change in seat and pedals so Brendon Hartley could get an afternoon spin gradually died away when the covers remained firmly up in front of the Toro Rosso garage.
Toro Rosso remained quiet on the issue throughout the afternoon, prompting whispers of a potential problem with the Honda power unit.
However, shortly after the checkered flag waved at the Circuit de Catalunya, Toro Rosso revealed it was an issue with the brake system that hindered their running.
That’s the day finished 🏁
— Toro Rosso (@ToroRosso) March 6, 2018
Honda, meanwhile, remain hopeful that Hartley will be able to get up and running quickly on Wednesday morning.
— Honda Racing F1 (@HondaRacingF1) March 6, 2018
Honda technical director Toyoharu Tanabe added: “Our programme this week is more race focused.
“Unfortunately we lost some track time, stopping running in the afternoon because of an issue with the car.
“Identifying problems like this is what testing is for and we will make further preparation to make up the lost time over the remaining three days.”