[m463]

press the start button without stepping on the brake

Unfortunately it is difficult to KNOW you are in accessory.

There is a tiny battery symbol on the dash and/or the traction motor indicator is off (car symbol with arrows underneath). This is non-obvious and lost in the other indicator lights.

You will eventually find out (like a regular car) because climate control will not change the temperature, but the fans will blow and the 12v battery will drain.