German engineering ain’t what it used to be.

Melissa Marsala, a Mercedes owner from Cape Coral, Fla., was driving her 2001 ML430 at about 45 mph down a main thoroughfare, when her vehicle suddenly went into braking mode. The two vehicles behind her in the inner left lane slammed on their brakes to avoid a collision, and Marsala was able to ease the bucking vehicle onto the grassy median that divided the roadway.

“It terrified me,” Marsala recalled. “There was no reason for the brakes to engage. I was trying to come to a full stop but the car went boom-boom-boom-boom. It happened in an interval that was so quick. The car was skipping, smoke was coming off the wheel wells and you could smell the rubber burning. I veered it right into the median strip and it stopped itself.”

Those moments of sheer fright were courtesy of a malfunctioning yaw sensor – a problem primarily in the M-Class – well known to Mercedes, some M-class owners and the National Highway Traffic Safety Administration’s Office of Defects Investigation. In 2007, NHTSA opened and quickly closed a Preliminary Evaluation into sudden unintended braking involving about 100,000 MY 2000-2001 M-class vehicles, without taking any action.

In May of 2007, Mercedes explained it all away to ODI at a presentation in which the automaker simulated electrical faults in the yaw rate sensor and showed how “the ESP [Electronic Stability Program] system is programmed to diagnose electrical faults and that brake applications resulting from yaw rate sensor electrical faults are very short in duration (0.3 seconds or less) and don’t affect vehicle control or stability.” NHTSA’s Vehicle Research and Test Center was unable to duplicate the problem in a vehicle that had experienced multiple events; and ODI’s attitude was: no documented crashes, low complaint rate, no problem. Continue reading →