Red Bull's Max Verstappen has reverted to a previously used power unit after Honda discovered an "anomaly" in the data of his Formula 1 car.
Under parc ferme conditions Verstappen has swapped back to a previously used V6, turbo, MGU-H and MGU-K. No penalties are associated with the changes.
A Red Bull spokesperson told Autosport: "After spotting an anomaly on the data from Max's PU we decided it would be best to change it to a previously used PU for the race and were granted permission to do so by the FIA."
The Red Bull mechanics have also changed the left hand side chassis loom, the brake-by-wire unit, and both the left and right hand side axle ends.
Verstappen noted early in Saturday's qualifying session that the car had felt "weird," and the last change may be related to that.
"I went through Turn 2 and I could see the left-front wheel coming up - which was very odd - but it didn't happen afterwards," the Dutchman said after qualifying.
"They checked everything, and everything was fine, so I honestly don't know what felt so weird. It was quite gusty out there as well. Bit odd but luckily it didn't come back."
He added: "I felt very happy in the long run yesterday, with the balance of the car and the wear of the tyres as well.
Of course, I hope that I can be close to [the Mercedes] and put the pressure on."
Meanwhile Sergio Perez has taken a new Mercedes energy store and control electronics.
These are the final units that the Racing Point driver can take this season before penalties kick in, and the change has been made unusually early in the season.
Lewis Hamilton has replaced his front left tyre in his starting set from Q2, while Alex Albon has changed both his rears.
Drivers can take tyres of a similar mileage if they are deemed to be damaged by the team, under approval of the FIA.
Both Renaults have also undergone a number of changes, with Esteban Ocon - who had a heavy crash in FP3 - taking a new steering column, and Daniel Ricciardo a new floor and some clutch elements.