no crank, no start

Question by bruceis65 posted 5 months ago in 2007-2012 (X164)

Seemingly there's five "try this" for every one code. Confusing to a novice like myself. Likely my question(s) won't be succinct but I'll try.

My 2009 GL550 has been slow to start for a month. It did start so my worry flag was only at half staff. Parked it one evening and two days later when I turned the key within three seconds and a half hearted turnover, nothing. All dash lights illuminate. Two fuses don't work even after replacement. Both 40A, secondary air pump and airmatic control unit height adjustment. I don't sense this is the no crank no start due to these two fuses. I'll address this when the car is running.  

Using my iCarsoft MBII I have codes that indicate: ESI 900516 Terminal 30 not present. Also C312: signal stop lamp switch on CAN bus not present or faulty. I read that the C312 problem could indeed be underlying the no crank no start. The ESI 900516 is a more likely culprit.

My question being old school as I'm old. Could the starter be the real cause of the no crank no start problem. It was after all showing signs of weakness for a month.