4X4 LIGHT - Please help!

One day I noticed my blower fan not able to adjust speed, I YouTubed and found how to check the resister.

Removed my glove box, found the resister, disconnected the harness as instructed and came to realize I wasn't able to reach the two bolts that were securing the resister in place.

I then gave up and went inside for couple hours and then had to go somewhere and I went to start my Tahoe and all the dash lights started acting strange by blinking abnormally. Turned off the power and plugged in the harness and started the truck and now the Service 4X4 light is on.

(The blower issue seen 2 mechanics. 1st one said the wiring started smoking or something when he went to work on the blower motor and sent me to an electrical mechanic. Mechanic 2, replaced the blower motor and now works fine; also diagnosed the 4x4 and evidently it's the transfer case "so he says")

I checked all my fuses and are good.
The lights work when power is on before turning over the engine, then no lights at all on the 4x4 buttons when engine is started, just Service 4x4 light in dash.

4x4 was fine until I started troubleshooting the blower issue and messed with that harness.

I have a 1999 Tahoe LT

Thank you

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Best thing to do is to get the code that's triggering the "Service 4x4" light. You'll need a scanner like a Tech 2 that will read those types of codes. They typical engine-only OBD scanners won't read them. Sometimes Advance Auto or other parts places will have the more advanced scanners to borrow and use in their parking lot.

Thank you much!
If you would help me out a little more on what I'm looking for - like do I just write the code down or will it tell me more detail, what do i do after that?
And have you heard of this problem before?
I apologize, I'm not too mechanical.
Thanks

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NO GO on a Tech2 reader checked 3 different places and no one has one. Although, I checked the readings anyhow with the ODB II since my Service Engine light is on also (which is fairly new) and said it was a couple of O2 sensors which isn't the end of the world, but nothing on the Service 4x4 light.

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Probably not your problem but mine was acting up and i just replaced the switch. Fixed it

It doesn't HAVE to be a Tech 2, just a code reader that will see the 4x4 system codes. I don't think the little cheap readers do that, but I might be wrong. Never tried my Actron reader in the Hoe since I have a Tech 2.

I'm not one to just throw parts at it, I prefer an educated solution, but whatever works for you.

Try a repair shop, they should have a capable scanner. Tossing the guy a few bucks wouldn’t hurt.

Once you have the code, there are GM diagnostic tables that go through the troubleshooting.

Yes, if you can get the code that will help you diagnose the system. Is your 4wd system currently working? My service 4wd light came on a couple of weeks ago but the push button system and 4wd was still functioning. My situation ended up being the lock solenoid in the encoder motor - which explains why the transfer case would occasionally shift into neutral while driving. When I pulled the code, it was an error in the lock solenoid...