Renault's steering wheels and Electronic Control Units (ECUs) have been impounded by the FIA at Suzuka following a protest from the Racing Point team.
The protest alleges a breach of Formula 1's sporting and technical regulations, as well as the FIA's International Sporting Code.
The complaint accuses Renault of utilising a "pre-set lap distance-dependent brake bias adjustment system" on the cars of Nico Hulkenberg and Daniel Ricciardo during the Japanese Grand Prix.
The pair had a dismal time in qualifying on Sunday morning and qualified in 15th and 16th place respectively, but fared much better in the afternoon race.
Ricciardo took sixth place following a double penalty for Ferrari's Charles Leclerc, while Hulkenberg also finished in the points in tenth position. That's helped them firm up their grip on fifth place in the constructors championship.
But Racing Point has reportedly presented a 12-page dossier to the stewards, who conducted a preliminary investigation and met with representatives of both teams as well as one from the FIA technical department.
The stewards determined that there were valid grounds for the complaint, and instructed the FIA technical department representative to seal and impound the ECU of both cars, plus their steering wheels. The ECU is a standardised component developed by the FIA on behalf of the teams.
There will now be a "detailed analysis of those pieces" and the "hardware, software and data associated with them". Findings will be presented in the form of a written report to the stewards at a future date to be determined, which will be reviewed against the “potential technical infringements detailed in the protest.”
In a statement Renault said it acknowledged the protest but added: “Renault F1 Team intends to use this recess to prepare an equally detailed case to rigorously defend its position."
The FIA document about the protest gives no further details about the complaint. In the meantime, the current provisional Japanese GP race results are unchanged.