This problem was the principle theory explaining the rash of “unintended acceleration” cases that plagued Toyota in 2009 and 2010. Toyota and Mercedes both argue that a floor mat could get in the way of the gas pedal, and that it could offer enough resistance to prevent the pedal from releasing when the driver takes his or her foot off.
Obviously, a car with its throttle stuck partially (or fully) open does not make for a good situation. If a car does accelerate for no reason, drivers are usually told to slow it down with the brake pedal and shift into neutral. The brakes on most modern cars can overpower the engine in emergency situations.
However, Mercedes owners don’t have to worry about any of that. The M-Class has a brake-override system, which cuts off the throttle when the driver presses the brake pedal, even if the gas pedal is trapped by a wayward floor mat. The system can automatically throttle the engine back to idle speed; all the driver has to do is brake.
An even better solution would be to remove the floor mats and not put one’s fate in the hands of a computer. The recalled mats are optional all-season ones; the M-Class’ stock mats are not affected.
Because of the brake-override system and the simplicity of the fix, Mercedes is taking its time with this recall. Owners will be notified in September, at which time they can take their SUVs to a dealer for new mats. Until then, Mercedes is advising its customers to remove their all-season mats.
Cars are incredibly complicated machines, but even the slightest details can set things awry. From using the wrong glue on fender linings to selling misshapen mats, these details can cause big problems. This time, the solution is pretty straightforward, and if all else fails, there’s a very complicated system of electronics waiting to bail drivers out of trouble.