2001 yukon 4wd not working? any idea's

Hey, i have a 2001 yukon xl, last winter it would not shift into 4wd the light just blinks.. i have tried driving 3-5 mph and going for 4 lo and all other metheds mentions in the book. my brother has a suburban basicly the same car, on his i can hear the shift moter kick in. on mine it doesnt make that noise.. i just replaced that motor.. and still nothing. im out of ideas and when i went the GMC they said $700 to look @ it... any ideas please and thanks

Magicaljerky

This mite work. On my 03 chevy trk it has stoped twice and just before I went to take it in and spend a lot of money for nothing. I tried removing the battery cable for a few minutes and reconect it and the four wheel drive started working again. I think its some kind of mileage thing that wants you to take it in to have your 4 wd checked out. let me know if this helped:2cents: