It’s a mystery. I can’t find it in any manuals that I can get my hands on. Dealers don’t know. It’s a chasis cab so no other doors externally to check. There are no loose wires coming from the cab loom into the chasis that I can see. I wondered vacuum related ?
Speed Limitation Device..... It says in my books that it is a 'Malfunction - road speed limiter' (page 83). That's as written in the Operating Instructions book for Medium-heavy range (MK) and Heavy-duty range (SK) trucks. It goes on to say on page 83 that it should stay on until approx 7km/h is reached and then go off.. If it doesn't then there is a fault with your limiter and you need to visit your local MB dealer.