Toro Rosso debuted its STR11 in an interim blue livery in Spain on Monday but Carlos Sainz Jr. was halted by a suspected gearbox problem.
Sainz racked up 55 laps in his new car but sat out the latter stages of the afternoon session at the Circuit de Barcelona-Catalunya on an unusually quiet opening day of testing.
"We were all obviously very much looking forward to today and it was a great achievement to drive out after not the easiest of winters," Sainz said, referring to the team's late switch to Ferrari power.
"The team has done a great effort and today was quite a decent first day.
"We managed to have a very clean morning and it was also being a smooth afternoon up until we suddenly had to stop the car…
"So we had to unfortunately call it a day, but up until then it was all going perfectly and I felt good in the car."