I'm sure this is somewhere on the site but I couldn't find it with the search function. I used several different search terms and couldn't find it. Anywho

Service 4wd light comes on within a few miles of driving after a cold start. The 2wd light on the button stays lit most of the time. Sometimes it goes out, sometimes it's dim, sometimes even flashes for a couple of seconds. I've cleaned, greased and re attached the ground wires on the frame that I've heard about. That didn't fix it. The 4hi works, but it won't go back to 2wd on command until it wants to. Not going to attempt 4lo for fear that it'll get stuck and it won't be drivable on the road.

I've read that it could be the module in the dash with the buttons, could be the tccm, could be the actuator on the axle. Not 100% but fluid may have not been changed, but I doubt that the fluid would be triggering a problem in the buttons like this. What is the cause of this?

I have enough money to buy new buttons module, tccm and actuator. That's not an issue. I'd rather avoid that if possible.

2001 Suburban 1500 LS, 183k miles

 

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Fixed. Turns out it was the switch in the dash. Replaced it and the service 4wd light hasn't come on again yet. Confirmed that the switch works. It goes in and out of 4wd on command now. The lights on the switch stay on for whatever mode it's in at the time.