(Refiles to add dropped word in first paragraph)
* 17,600 Fusion, Milan hybrids may have software glitch
* Hybrids in question were built on or before Oct 17, 2009 (Adds details on affect of regenerative brake cutting out, background on Ford and Toyota)
DETROIT, Feb 4 (Reuters) - Ford Motor Cosaid on Thursday it would fix up to 17,600 hybrid sedans that could suffer braking problems as its largest rival, Toyota Motor Corp , grapples with a reported braking problem on its market-leading Prius hybrid.
The Ford decision came the same day U.S. 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.
The automaker received a handful of reports about the issue and had heard reports of one minor accident, but no injuries as a result, Deep said.
In Consumer Reports' case two weeks ago, a test engineer was driving a Fusion hybrid the influential nonprofit magazine bought last year for a review published in September when the braking incident occurred. The magazine has maintained its recommendation on the Fusion hybrid after the incident.
"Being a customer satisfaction program I think is OK in that they do have brakes if you push hard enough," Champion said. (Additional reporting by Bernie Woodall, Kevin Krolicki, Soyoung Kim and John Crawley; Editing by David Gregorio and Carol Bishopric)
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