Fernando Alonso is to revert to Honda's 'Spec 2' power unit for the remainder of the Austrian Grand Prix weekend, after an MGU-H problem was detected with his 'Spec 3' unit.
Honda introduced the upgraded version for this weekend's event at the Red Bull Ring, having trialled the updates during free practice at the preceding round in Azerbaijan.
Alonso placed eighth in Friday's second session, with team-mate Stoffel Vandoorne 12th, and Honda was cautiously optimistic over the gains.
However, an MGU-H issue was detected on Friday evening, and Alonso's power unit has been changed, meaning he has gone back to the 'Spec 2' Internal Combustion Engine.
All of the newly fitted components have been used during previous Grands Prix, meaning that there will be no grid penalties.
Team-mate Vandoorne will continue to use the 'Spec 3' power unit.
