We recently experienced a perceived brake failure with our 2010 Ford Fusion Hybrid. We told Ford Motor Company about it and within days Ford instituted a "Customer Satisfaction Program," essentially a brake-system software fix, available free to all owners of Ford Fusion and Mercury Milan Hybrids made on or before October 17, 2009. (The build date can be found on the driver's door jam.)
Here's what happened:
As one of our senior engineers slowed for a stop sign at the turnoff to our test facility in East Haddam, Connecticut, the brake pedal went unexpectedly further down than normal but the car barely slowed. He zoomed through the turn, with brake-system warning lights illuminated on the dash. The car more or less coasted to a stop, with what our engineer described as minimal brake feel.
After switching off the engine and then restarting it, everything returned to normal—no warning lights and full braking capability. We then took the car to our local Ford dealership, where the service manager told us that a Technical Service Bulletin covered this problem.
The bulletin in question, coded TSB-09-22-11, described a situation much less scary-sounding than what we experienced. To paraphrase, the brake system could sometimes sense a problem where there was none, causing the electronic braking system to revert to conventional hydraulic brakes, including ABS. If that happened, the braking system would revert to a backup conventional hydraulic mode that preserved braking capability, but the pedal will drop over an inch. When the engine is restarted, the electronic braking system would resume.
The factory representatives confirmed that our car's brakes had experienced a fail-safe mode incident, but they didn't see a brake failure. They brought our car back to the Consumer Reports' Auto Test Center with its electronic brake module disabled so we could see for ourselves. Our test director and senior test engineer tried it out. The pedal travel was long and the pedal felt mushy underfoot, but when the pedal was pushed firmly down, the brakes did stop the car effectively.
When that module cuts out, the brake pedal needs to be pushed just over an inch farther down than normal before the conventional hydraulic system applies the brakes. Could our test engineer just not have pushed the pedal down far enough when the electronic module quit? He certainly didn't think so at the time, but that would at least explain why he thought he had no brakes.
Ford engineering representatives explained that the software threshold for establishing a fault in the regenerative brake system was set too sensitively, causing the system to transition to conventional brakes when it was not necessary.
Our case may be rare but is not unique. We located five other similar accounts of perceived brake failure. One report was filed with the government's auto-safety complaints database www.safercar.gov and others with an enthusiast sites, such as fordfusionforum.com. Their comments included these:
"...while driving down the road the brakes suddenly hit the floor and there was minimal resistance."
"...turned off the parkway into Manhattan and the brakes failed! The car was on, drove and steered fine, but there were no power brakes."
"...moving at around 3 miles an hour and I press the brakes and nothing. It was like you never touched them."
None of those cases reported a crash or injury.
Putting a stop to the brake problems
Whether our engineer, a 30-year testing veteran, hit the brakes as hard as he should have or not, we believe other drivers may react similarly. We are glad Ford has initiated a repair program and will notify all known owners by mail starting in early February 2010.
Ford estimates that approximately 18,000 2010-model Ford Fusion and Mercury Milan Hybrids could be vulnerable to the electronic brake-software glitch but only a tiny fraction will ever exhibit it. Ford explained, "The software threshold to transition from regenerative brakes to conventional brakes can cause the system to transition to conventional brakes unnecessarily."
In a statement, Ford said, "We have received reports that some drivers have experienced a different brake feel when the hybrid's unique regenerative brakes switch to conventional hydraulic braking. They may initially perceive the condition as loss of brakes even though the vehicle has full braking capability. When this occurs, our system maintains full conventional brakes and full ABS function."
Ford added, "There have been no injuries related to this condition."
If you own a Fusion or Milan Hybrid made on or before October 17, 2009 we strongly recommend that you have your local dealer perform the brake-system software update specified by Ford's "Customer Satisfaction Program 10B13."