Ford Motor Co said on Thursday it would fix up to 17,600 hybrid sedans that could suffer braking problems.

The Ford decision came the same day US safety regulators opened a formal probe into consumer complaints that brakes on Toyota's 2010 Prius had momentary problems after motorists rolled over potholes or bumps, allegedly causing four crashes.

Toyota has faced criticism for not notifying consumers about suspected problems with the brakes on its Prius right away, but Ford waited until Thursday to announce possible braking issues though it had known about them for months.

The Ford announcement came as Consumer Reports said one of its engineers ran a stop sign in a residential area when the brake pedal on a Fusion hybrid sank further than normal and warning lights lit up the dashboard. The car coasted to a stop with minimal brake feel, Consumer Reports said.   

The National Highway Traffic Safety Administration database has a complaint from a motorist claiming that the Fusion hybrid brakes offered minimal resistance. The administration has no formal investigation into the Ford vehicles.

Ford said a software glitch on Ford Fusion and Mercury Milan hybrids built on or before Oct 17 could cause drivers to perceive a loss of braking as the car shifts unnecessarily from regenerative braking into the conventional mode.

Ford was not treating the matter as a full-on recall because the automaker did not see the result of the software glitch as a brake failure. Ford said on Thursday it would upgrade the software on the vehicles and expects to notify customers by mail that the fix is available at dealerships.
   
Consumer Reports said that with the regenerative braking disengaged, as happened in the incident near their track, the brake pedal needed to be pushed more than an inch farther down to engage the conventional brakes.

"The fact that the pedal goes away is I think for many people very disconcerting, but the fact is if you push hard you do go in to full braking," said David Champion, director of Consumer Reports' auto testing center.   

Ford spokesman Said Deep said the automaker started to see indications of the glitch in October and had notified dealers of the possibility and a software upgrade to resolve it.

"It's a customer satisfaction program because the car still maintains ... full conventional braking," Deep said.-Reuters