01 Yukon 4x4 selector switch has no light indication

[budmaniac]

The indicator lights don't show if I am in 2 wheel drive or 4 wheel drive. And I cannot engage transfer case to go into 4x4. I have changed out the switch 2x already. After the switch change out, the lights would work for a few weeks, then go out. From all the posts from other owners with this kind of issue, some change out the front axle differential actuator or the transfer case encoder motor. So my question is how do I know which one to replace in order to get the 4x4 to engage, and for the selector switch to show what operation is the transfer case is in, eg: 2x4, or 4x4??

 

[YukonXL04]

When I had my 2000 4x4 Sierra the encoder motor went out first, then a year later the switch. There is a way to test each one, I forgot how but just do a little google searching and you should be able to find it.