my 2008 Chevy Duramax has a service four wheel indicator on, there is no light on the selector switch ,replace switch still doesn't work .
checked fuses, good. Ground wire good, still no light on selector switch,
What code are you getting? C0569?
Is so try the motor learn procedure:
1. Turn ignition switch to the Accessory position.
2. Place 4WD switch to "2 high"
3. Turn switch past "4 low" to neutral and hold for 30 seconds
4. An audible noise from the motor indicates the learn procedure was completed.
Sometimes it's hard to find a problem because of a loose connection of the wires/sensors. So when you scan the connection may be fine and it wouldn't throw a code, but a minute after the code will show up.