Both Toro Rosso drivers will use updated Honda turbocharger and MGU-H components in the Bahrain Grand Prix after Pierre Gasly's engine failure in the Formula 1 season opener.
Toro Rosso's partnership with Honda began well with strong reliability in testing but its competitive debut in the Australian Grand Prix was hit by an early engine-induced retirement.
Toyoharu Tanabe, technical director of Honda's F1 project, explained that the internal combustion engine on Gasly's car was damaged by a problem with the turbo and MGU-H.
Honda has modified the turbo and MGU-H ahead of this week's race in Bahrain to avoid a repeat, and will fit those parts to Gasly's car and his team-mate Brendon Hartley's as a precaution.
Gasly also needs a new combustion engine after the damage incurred in Australia.
This season F1 drivers are limited to no more than three combustion engine, MGU-H and turbo components and will incur a grid penalty for using any more fresh elements.
That means if Honda cannot salvage the previous components, Gasly only has one more free change of those parts over the remaining 20 grand prix weekends
Hartley is in the same position if he needs to replace the MGU-H and turbo, but still has the combustion engine used in Australia.
"Replacing components for the second race is obviously a difficult decision and not ideal, given that the number of power units and ancillary components is now limited to just three per season," said Tanabe.
"However, we believe this is the right way forward and we will continue our development in order to ensure the same issue does not reoccur.
"Although Sakhir is a tough track for the power unit, we hope to move on from this difficult moment, as we focus on this race and those that follow."
Neither driver's engine requires a change of energy store, control electronics or MGU-K, so both can still change each of those components once without triggering a grid drop.