service 4wd light on

Hello,

The 4WD error light can be illuminated when the system detects a fault within the four-wheel drive system.
It can be due to few different reasons.
It can be a faulty transfer case shift module, bad switch, inoperative transfer case, it can also be due to a wiring issue.
I have included the wiring schematics for your reference.

https://www.2carpros.com/articles/how-to-check-wiring

I have attached the diagnostics steps for the 4WD error light (look below).

Please let me know of any questions.
Thank you.