Honda reveals cause of "extremely challenging" Aston Martin F1 engine issue

Honda is working to solve crippling vibration issues in time for Formula 1's 2026 season opener in Australia after a disastrous series of tests with Aston Martin.

Aston Martin and Honda suffered a rough start to their partnership in pre-season testing, with minimal mileage at the Barcelona shakedown after the AMR26 was delivered late. A number of issues on both the car and power unit side then further limited running across the two test weeks in Bahrain, with Aston Martin's total distance of 2115km just over a third of the mileage covered by the likes of Mercedes, Haas and Ferrari, and just over half that of the next team with the fewest laps, Cadillac.

As Aston is Honda's only F1 partner, that means mileage for the new Sakura power unit has also been well below that of its rivals. On the final day of the second Bahrain test, Aston Martin had to end its programme early as it ran out of spare batteries, with the team only running six install laps.

Speaking to the Japanese media, including Autosport's Japanese sister edition, Honda provided more details on its woes, explaining that excessive vibrations coming from the V6 combustion engines kept wreaking havoc on the battery.

"The abnormal vibrations observed during testing caused damage to the battery system, which was the primary reason for the stoppage," said Ikuo Takeishi, head of the HRC four-wheel racing department, about Fernando Alonso's curtailed fifth test day in Bahrain.

"We stopped the car because we felt it shouldn't continue running in that state. It wasn't that an accident was imminent or anything like that, but we stopped the car because it was dangerous.

Fernando Alonso, Aston Martin Racing

Photo by: Alastair Staley / LAT Images via Getty Images

"The PU side is naturally investigating the cause and working on countermeasures, while simultaneously implementing measures on the chassis side. Specifically, we are currently using the Sakura battery on a bench with the monocoque mounted, actively running multiple countermeasures while conducting vibration countermeasures and analysis."

Takeishi said the findings meant it is too early to say if there is an actual issue with its battery design itself. But because he believes the cause of the crippling vibrations is not down to one single part, Honda is concerned that there's no guarantee of an easy fix.

"The vibrations caused damage to the battery, so we cannot say whether the battery itself is the problem," he elaborated. "You could think of it as the battery pack being shaken within the vehicle body. Essentially, the area where the battery pack is attached is vibrating. Had this been within expectations, I believe we would have made further adjustments. As it stands, I suspect we've encountered a rather challenging situation.

"For instance, if the cause were pinpointed to something like the transmission or the engine, it would be much easier to tackle. However, I suspect multiple components are interacting to generate the vibration. Given that, it's unclear whether fixing one part alone will resolve it, so we can't rule out the possibility of this dragging on. That said, purely in terms of determination, I'm absolutely intent on fixing it quickly."

It means that Aston and Honda will likely still be compromised to a significant degree in the opening stages of the 2026 season, with Honda hoping to get the car "into a competitive state" by the Japanese Grand Prix at the end of next month - the third race of the campaign.

"I'm aiming to reduce the vibration before the season opener, but I intend to get the car into a competitive state before Suzuka," Takeishi said.

Lawrence Stroll, Aston Martin

Photo by: Kym Illman / Getty Images

Honda is confident its power unit will be in a much better state once its vibration problem is under control, but Takeishi acknowledged the Japanese manufacturer is in no position to "talk actively about performance" right now.

But HRC boss Koji Watanabe said Honda and Aston Martin would work serenely to get over the difficult start to their partnership.

"The recent pre-season tests in Barcelona and Bahrain were, frankly speaking, extremely challenging for us," Watanabe said. "We were unable to achieve the performance levels we had anticipated, and a complex set of issues became apparent. However, these tests were also a crucial process in that they allowed us to visualise these challenges.

"There may be various issues on both sides, but we are aiming for a long-term partnership, and at this stage I believe we are united in our desire to resolve matters as one team.

"I have had very positive discussions on the phone with chairman [Lawrence] Stroll and [Adrian] Newey about how to resolve the situation. With the season opener approaching, it goes without saying that we will do our utmost to ensure we are ready to race in Australia.

"Naturally, the drivers testing are understandably frustrated, but we can only address that through performance."