The matter - which applied to all four Honda Civics, including the Zengo Motorsport entry of Ferenc Ficza - was not resolved overnight, which meant the results of qualifying and both of Sunday's races would remain provisional.
But on Sunday the stewards confirmed the investigation had been concluded, deeming that no further action need be taken.
The stewards' statement, released during the first race at the Hungaroring, said: "Following the Technical Delegate Report N.3 about the flat bottom of the cars 5, 12, 18 and 55 of the manufacturer Honda Motors, the stewards investigated the matter and found that according to Appendix J Article 263 of the ISC they are in compliance with the current regulations."
Ficza was the only Honda driver to score in the opening race, finishing ninth to claim his first points in the WTCC.
Rob Huff was overtaken at the start of the final lap and finished 11th, one place ahead of Tiago Monteiro, while Norbert Michelisz pulled up on the first formation lap after a turbo problem.
Honda confirmed that having recovered his Civic, it has broken parc ferme regulations to repair the problem.
Should Michelisz make the start of the second race, he will line-up at the rear of the field as a result.
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