service 4 wheel drive

montuck2montuck2 Member Posts: 1
edited June 2014 in GMC
2oo7 yukon 971 miles "service 4 wheel drive light"
came on, 2 days at dealor, calls to GM, tenative diagnois, speed sensor unit(?) part on "back order ok to drive." Back at home pulling out of drive way, air vent fan slows down and "on stary ready" voice comes on, applantly goes off and then the air vent fan resumes speed. Any help appreceiated.


  • 99yucon0799yucon07 Member Posts: 1
    Has anyone had this light come on? It does not come on all the time only once in a while. Thanks.
  • mrenvoymrenvoy Member Posts: 1
    my 2002gmc envoy does the same thing and is currently in the shop now for that reason. when my light comes on no 4 wheel drive at all. i thought it was intermitting but i realize its only when the vehical gets wet or goes throught the car wash. they say its possible a modular possible getting wet by water getting in through the vents under the winshield wipers.
  • vinnyveevinnyvee Member Posts: 4
    i have an 07 yukon and about a month ago the service 4 wheel drive light came on i shut the truck off and restarted it,the light then went out.ive had no problems since any body know why it happened?
  • zwitter153zwitter153 Member Posts: 5
    I have an 07 Yukon with 20581 miles. I have just noticed the same pulsing problem as well. I had an 04 Yukon and put nearly 60K miles on it and never had any rotor problems.
  • zwitter153zwitter153 Member Posts: 5
    My 2004 Yukon did the same thing. GM repalced the "encoder" motor in the trans. It tells the computer what mode the trans is in. It is not monitored by the system same system that stores codes, so you cannot run any diagnostics on it. It either works or it doesn't. I would go back to GM and demand they replace it before your warranty expires.
  • gauberggauberg Member Posts: 1
    I've gotten this message before, but usually if I turn off the engine, and restart it will usually go away. Or sometimes I'll switch it back and forth from 2 weel to 4 weel, but this time it won't give me access to the lighted buttons to do this. I had it to service for this problem, but they never came up with anything. I wonder if I were to disconnect the battery, and then reconnect would this reset the computer, and allow the buttons to light up again so I'd be able the excerise the drive by switching from 2 weel to 4 weel and so on. Any Ideas?
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