My Max had Error 15 from the very beginning.
I noticed that the brake wire was very porly adjusted - I hade to pull the brake lever all the way in to activate the brakes.
After adjusting it , the error only appear sporadicly.
When it does I only have to activate the brake handle for it to go away.
It becomes more frequent over time, but a reset procedure seems to make it better for a while.
I suspect that there is no problem with the trottle because the error will appear on cruise control or with me having the trottle on full gas.