I did not tried to disconnect the negative terminal on my battery, I will do it today to see what will happen. The dash light is also off, so all light off, no power for windows or mirrors. Even if I dont turn off the engine and I just put the car on parking sometimes everything is coming back. The scary part is when I was on Highway and I have to change lines to the shoulders without signal and light on brakes:(. I got yesterday a ODB scanner and I will have it always conected to the car and to my cell phone so hopefully I will get a code when this will happen again.