M2.0 has several low-power options. One of them is called:
"J1850 / ISO 9141 Low Power Control"
We have 2 microcontroller-controlled switches that allow "+12V_SW" and "+5V_SW" to be powered on or off depending on conditions.
The signal "J1850_9141_ON" controls this and is connected to the SAM3X pin number 120 (PB5)
Here is the code to turn on and off the 12V and 5V rails: