At my wits ends: 2013 Stelvio Not Starting

[PJPR01]

Having read thru all of the technical items....I would try draining the tank of the old gas completely and put in fresh gas.  Once on my Norge the bike started sputtering very badly leaving a rally in Kansas about 15 minutes after tanking up...it took me about an hour to get to a new gas station in rural Oklahoma and I put in some gas treatment and within a few minutes, the bike was firing smoothly again.  Since you're at home, try draining the tank completely, and load it up with some 93 Ethanol free if available or at the very least a can of gas treatment.  

Since you've checked all the fuses, it's sparking and fuel is squirting out of the injectors, I'm guessing your gas is not igniting.

[pete roper]

Any odd behaviour from the dashboard? Does it blank out when the engine is cranking?

[Pressureangle]

2 hours ago, Kuni0 said:

I performed the test in this video here (start of the test at 2:00 timepoint). Even though it's for a car, I don't see how it'll be much different for a motorcycle. 

Instead of seeing 5V for the high and low signal, I saw 2.5 and 1.5 V. I tested the ground per the procedure in the video and got exactly 12.6V

That sounds to me like you're going to have to resign yourself to 'search and destroy' mode. Every connector in every relevant circuit needs to be inspected and cleaned (Kaig DeOxit, aerosol on Amazon) 
I like to start from easy, working as necessary to hard; the suggestion to drain the fuel is not a bad one. I had enough water collecting in the injection hoses/barbs to give me fits a couple seasons ago. But since you know you have a voltage issue, the only thing remaining is to find the poor connection, or prove the ECU to be the problem by the test above- it isn't clear if your low voltages are at the sensors or actually at the ECU pin. 
Sometimes it be like that. 
Do you have a good clear schematic of the wiring for your particular bike?

[Kuni0]

This is the schematic that I've been using. It's for a 2012 Stelvio. Thankfully it's a very direct connection to the ecu. 55 is the cam position sensor I believe (it's labelled as 'Pick-up' sensor)

 

2 hours ago, pete roper said:

Any odd behaviour from the dashboard? Does it blank out when the engine is cranking?

The dashboard blanks out sometimes when the engine is cranking, but not 100%. The big "SERVICE" sign pops up sometimes, but again not 100% when I turn on the ignition. 

Bad gas was put as an option, but I'm doubtful of that since I filled up at the same gas station as my girlfriend and she had no issues with her bike (Yamaha MT-07) on the same gas. Regardless, draining the old gas and putting new in should probably be on the list of things to do at this point. (no-ethanol gas isn't an option here in California really unfortunately)

[pete roper]

If the dash is blanking out it means voltage is marginal. The dashboard has a built in failsafe protection that if the battery voltage drops below a certain figure, (9V? Can’t remember off the top of my head.) it will abort the start and kill all power to the ecu to protect it from voltage spiking if the engine does start. The ‘Service’ warning will sometimes appear if the voltage drops to close to that critical point and it may also trigger various error codes in the dash and ecu. The voltage drop is due to the current demand from the starter which is very high and if there aren’t sufficient CCA in the battery it will drop below criticality.

Usually when the dash re-boots after this event you’ll get a code appear on the LCD screen ‘AMG’ something or other which will appear before the tacho does its ‘Sweep’. Off you’re getting any of these symptoms it is most likely just a very tired battery and hopefully the ecu isn’t fried. It’s unlikely but not impossible. Thankfully ECU’s aren’t terribly expensive on the Bay of Fleas.