Honda is trying to find the root cause of the battery problems that forced Aston Martin's Lance Stroll out of the São Paulo Grand Prix at Interlagos on Sunday.
Stroll had more than one battery problem across the weekend, and his race ended before half distance. It was the latest in a long run of retirements for the Canadian this season.
A new problem
The battery fault is a new issue for Honda, which supplies Aston Martin's engines, and it came straight after a costly weekend in Mexico.
Honda knows what went wrong in Brazil but not yet why. Its lead trackside engineer, Shintaro Orihara, said the team must find the real cause for next year, warning: "Otherwise, we keep having the same issue."
Two cars out in Mexico
At the Mexico City Grand Prix earlier this month, both Aston Martins retired after five laps. The cause was cooling in the energy recovery system, the hybrid part of the engine, which Orihara said was under more stress than expected.
That meant Stroll has now retired from back-to-back races. Team-mate Fernando Alonso has had his own share of failures this year.
What happens next
Orihara said Honda's chief executive, Toshihiro Mibe, knows what is happening at the track and will take that back to Japan to help development. Aston Martin's next chance comes at the Las Vegas Grand Prix, the first of the season's last three races.
Race it on Late Brake
Interlagos, where Stroll's latest retirement came, is one of the six real circuits in Late Brake, the free browser game. Set a lap, then race your own ghost and see how close you can get to a gold medal time.
Sources: The Race, Motorsport.com, Autosport