Autotrac buttons not working

99 1500 Silverado xcab 5.3vortec w/autotrac
Does not engage 4x when I push the buttons. The amber led on the 2wd is faded most of the time and other times is normal brightness. Many
times the led on the 2wd button does not even light.
When I push any selection the amber led will flash on/off on that selection with no transfer case engagement and then revert back to the 2wd mode.
Where can I start?
John
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wrote:

say that it is your issue but I have replaced many. There has also been issues with the encoder motors on the transfer case as well as TCCM modules themselves. Try borrowing a switch from someone else's truck. The dash face just pops off and the switch easily pops out. There will also be a code stored in the TCCM if you know someone to retrieve it.
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John wrote:

John:
These switches are notorious for cold solder joints.
Resolder, pay dealer $50, or buy a new one at GM Parts direct.
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John wrote:

First place to start would be to see if there are any relevant codes. When the light flashes on/off and then reverts back to 2WD....it's telling you that it has attempted to shift but for whatever reason cannot finish the shift. It might be that the encoder motor physically is not able to shift the t/case, it might be that the front axle is not engaging (though you usually see the 4WD light flash continuously and not revert back to the 2WD position).
Unfortunately...it makes diagnosis so much easier on these vehicles if you have a scan tool.
Ian
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