Glad to see you here.
I tried to find the crank position sensor as you described, but couldn't find it from the rear of the engine. Instead I found one at the front of the engine, it's a kind of sensor with black heavy rubber gasket, it stays on a stand and is very close to a big rotor that driven by crankshaft, seems like it can detect the arrival of a piece of magnet on that rotor.
It locates very near to the belt tensioner, does it sound like CKP sensor to you? strange enough the Service CD also says the CKP sensor L5/1 for M119.97 engine is at the rear of the engine.
I tried to get used to it, but people always stare at me when I start the car, is this just because my 400E is attractive...
, I also worry that longer cranking can result in shorter battery life, 3 seconds means it consumes 3 times more energy from battery than normal cars, this is very bad in extreme cold winter here in Canada.