Why does the 4X4 switch does not light up

Hello,

If the switch does not light up, but the vehicle actually engages to four-wheel drive, then the issue is a bad switch.

If the light flashes and the vehicle does not engage 4x4 then the issue could be a faulty transfer case control module.
This can also be due to bad wiring.

Please let me know what you are experiencing.

https://www.2carpros.com/articles/automatic-transmission-problems

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.