Hi, I'm trying to replace my rear discs and pads on my 2013 slk250 CDI. I'm lead to believe I have to put the car in maintenance mode to get the caliper to wind back but can't seem to get it to work. Ignition is in position one, press and hold call answer and OK for 5 seconds but nothing happens. I've also tried call answer, call reject and the OK button. Help!