Japanese automakers are getting much-needed cover from an old standby, as the weaker yen helps prop up profits amid declining sales in China and the increasingly tough shift to electric vehicles.

Toyota, Honda and Nissan recently reported earnings that topped analyst estimates by 6% to 21% in the three months through June, and all cited the currency as a factor.

"If the yen stays low, they clearly benefit but it doesn't offset any other concerns," said Satoru Aoyama, senior director at Fitch Ratings Japan.