Here's what you do:
1. With the key OFF, make sure you are in PARK and your seatbelt is NOT fastened.
2. turn the key ON, press and HOLD the reverse override button, press and release the brake pedal and then release the override button.
3. WITHOUT pressing the override button, press and release the brake pedal.
4. repeat step two and turn off the key. (the key will already be on, of course)
You have four seconds to complete this procedure. And you probably will take a few trys, i have the Grandaughter do mine for me.