EA is the 'electronic accelerator', which is really the throttle actuator--the gizmo that opens and closes to let air into the engine. It is an electronically controlled electric motor coupled to the throttle butterfly shaft. It has a position sensor (variable resistor) for the throttle(accelerator) position, and another variable resistor (position sensor) for the throttle butterfly shaft.

You push on the accelerator--and first a micro switch on the top of the accelerator pedal opens and signals the 'engine control unit' to couple the 'electronic accelerator' motor to the throttle shaft (there is an electromagnetic clutch that disengages at idle or any time the computer says 'tilt'.)

The the EMU/EA checks the position of the throttle position sensor, checks the anti-slip, ESP,ABS systems, and determins if the throttle needs to be opened. If -yes-, then the EA computer sends a series of pulses to the EA motor, which rotates the throttle butterfly open. During this rotation, the EA/EMU checks the actual position of and speed of opening of the throttle butterfly shaft. This continues-always checking first, then opening the butterfly more-until the measured opening agrees with that commanded by the accelerator pedal. The EA/EMU then holds that throttle opening until the accelarator pedal moves (or one of the other systems like engine overspeed, transmission shift computer,transmission torque limiter, ABS,ASR, ESP calls for a reduction in throttle/torque/engine speed.

Fully closed to fully open takes less that 200 milliseconds. Open to closed is faster because the butterfly shaft is spring loaded to close.

The computer system has lots of safety features built in to prevent 'uncommanded throttle opening' that some cars seem to experience. Frankly, I don't see how it would be possible in the MBZ system unless a least 3 systems failed simultaneously--the accelerator pedal switch, the throttle (accelerator) position sensor, and the throttle butterfly shaft position sensor, AND the electromagnetic clutch beteween the throttle motor and the butterfly shaft.

A simple wiring short won't do it because the accelerator position sensor has a known range of values, and changed from (low to high) on pushing down on the pedal. The actual butterfly shaft position sensor has a different range of values, that changes in the opposite direction, so the system would detect the fault as soon as it a hppened and open the electromagnetic clutch.