Following complaints from over 100 owners, the National Highway Transportation Safety Administration (NHTSA) has opened a "preliminary evaluation" regarding a brake-related issue that can occur on the 2010 Toyota Prius Hybrid. This new NHTSA investigation is not related to the sticking throttle problems that prompted Toyota to issue a formal stop-sale/recall on eight other vehicles it produces.

NHTSA's statement indicated that this problem manifests itself as a momentary lag and/or surge during the braking process, specifically when the anti-lock brakes (ABS) are being activated while the vehicles are being driven over various kinds of uneven pavement. According to Toyota, "Some customers have complained of inconsistent brake feel during slow and steady application of brakes on rough or slick road surfaces when the anti-lock brake system is activated in an effort to maintain tire traction. The system, in normal operation, engages and disengages rapidly (many times per second) as the control system senses and reacts to tire slippage. A running production change was introduced last month, improving the ABS system's response time, as well as the system's overall sensitivity to tire slippage." While the fix is now in at the factory level, it's uncertain as to whether any of those vehicles have actually arrived at U.S. Toyota dealers.

The automaker has not stated how or when it will address the issue on any of the other approximately 37,000 Gen III Prius models sold prior to that date, although an inside source indicated that more information is likely to be released within the next 24 hours. However, Toyota has advised NHTSA that it plans to fully cooperate with all requirements of this new investigation. Whether the government finds it necessary to upgrade the status from preliminary evaluation to engineering analysis or ultimately recommend an actual recall remains to be seen. This latest NHTSA action comes one day after Japan's Transportation Ministry ordered Toyota to begin an internal investigation of the same brake-related problem on Gen III Prius models sold there following complaints from 38 owners in that market during the last seven months.

> Continuing Coverage: Kelley Blue Book Experts Weigh In on Toyota

> Toyota Owners, Shoppers: Sticking-Throttle Recall and Stop-sale Q&A

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