The 4Matic light comes on indicating the 4wd isn't working. I've been resetting it by disconneting the battery. After doing this the 4Matic works for about a week.

Last week it started working again on its own (light went out). The light came on again yesterday. The first time I started it after the failure the 4Matic light blinked 9-10 times. Hasn't blinked like that since. What does it mean?