Honda had completed testing with Toro Rosso using just a single engine during the second test but it was deja vu come Melbourne.
Toro Rosso suffered the first engine failure of their season after just 15 laps in Sunday's
Australian Grand Prix, the first major failure with Honda as their engine supplier. Pierre Gasly was forced to retire his car with an MGU-H issue, making an already disappointing weekend worse.
Having come to Melbourne with the hopes of challenging the midfield teams, Toro Rosso had a poor qualifying and lined up just 16th and 20th.
Honda F1 technical director Toyoharu Tanabe maintained the team had to keep a positive mindset going into Bahrain.
“It is disappointing that Pierre Gasly had to retire on lap 15 with an MGU-H problem,” he said.
“We now have to investigate the precise cause and then we have a few days of hard work to ensure we do not have a repeat of the problem at the next race.
“As for Brendon, after his early pit stop, because of a flat spotted tyre, he raced consistently, but with the difficulty of overtaking here he was unable to move up the order.
“It was a tough start to the season, however we have to move on from this and keep a positive frame of mind as we immediately start preparing for the second round of the championship.”