Four wheel drive fuse blown

Something is shorted in that circuit. The problem is finding it when a new fuse blows right away.

A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a twelve volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it is not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.

It could be the wire going to switch is touching ground someplace due to either something recently installed in dash and screw going through it or worn through. It is a pink/white wire that goes to switch.

Shorted O2 sensor heater feed wire is also possible. It's on the same feed as the 4WD system. I've seen them get melted to the exhaust when the plastic clip in the bracket fails.