The FIA has required Ferrari to submit to extra monitoring of its ERS system for this weekend's Monaco Grand Prix.
The SF71H has been fitted with an extra sensor after rumours that the team had found a way to get more energy deployment from the battery than is allowed under the rules.
Mercedes’ Niki Lauda had been one of the first to raise questions about Ferrari's approach to battery management. Its car has utilised a unique double-in-tandem battery since the start of the hybrid era in 2014.
Lauda had called on the FIA to rule on whether Ferrari's set-up complied with the rules, but the governing body has said that the twin-battery architecture was not illegal.
This year things stepped up with mutterings that Ferrari had found a way to use this architecture to briefly boost the energy flow beyond the 120kW limit, without getting detected by the standard FIA sensors.
FIA race director Charlie Whiting insisted that no evidence had been found of anything that circumvents the regulations. This weekend's extra sensor requirement is designed to definitively rule out any possible misuse.
However Ferrari's main rivals said they didn't think Ferrari was doing anything amiss, and insisted that they had confidence in the FIA's technical scrutineers.
“There’s obviously been rumours that no doubt you guys are cottoning onto as well,” Red Bull team principal Christian Horner told Motorsport.com.
“I’m sure the FIA have all the competence to be able to measure, administer and look at the car that’s presented for scrutineering."
“Legality topics come up regularly," noted Mercedes boss Toto Wolff. "It’s the daily business of the FIA to check what the teams do.
"It’s the obligation of the teams to comply with the regulations, and this is an ongoing process.
"“I have great confidence that with whatever issues are coming up, either the chassis or the engine, the FIA has been on top of it."
Sauber uses Ferrari customer power units, but team principal Frederic Vasseur said that it had not been asked to run the additional sensors.
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