Problems with 4X4 not working?

There are two different models of this. One is electronic shift and the other isn't. The electronic shift Does have a module. I am assuming yours does not. Check the items I've pointed out in diagram starting with the relay underhood center of cowl/firewall. Then check the others to see if they are getting power or not. It may be the switch on tcase so you'll get dirty doing this. You can use a test light or volt meter to do it. If the electrical works then it's either one of the switches or an internal problem in tcase.

Under lh side of dash and would have about 30 or so wires leading into it.

Have you checked to see if there is power to the actuator on the transfrer case?

If it went from 4 hi to 4 lo, the transfer case and shifter is fine. Check the actuator on the front drive axle.

Let me know what you find.

Joe

The common reason for this is the thermal actuator on the axle has failed. The original design on these was a part with a wax inside a tube with a heating element. When you shift into 4WD the element warms up, the wax expands and it puts the front axle interlock into the lock position. Over time the units heat up in summer and they leak the wax out. After a few years enough leaks and they don't move far enough to engage the axle. To repair it you unscrew the old actuator and replace it with a new one. There are conversion kits available for them to install a motor type actuator instead of the wax version.

Verify that when you select 4WD that power is going to the actuator. The wires can get corroded or break inside the insulation from flexing or right at the connectors. The Black wire should be ground and the Light Blue should be battery voltage when it is engaged. To test it you just need a test light. Connect it in place of the actuator. Fuse 24 powers the circuit. Power goes from it to the switch on the T-case. When you pull the lever that switch then sends power to the actuator. If you get nothing with it engaged connect the test light to ground and touch it to the terminal the light blue wire ends in. If it lights you likely have a bad ground sire. If not it is likely the switch. Just trace the power back.

First, if you have the electric shift 4wd, check to make sure the actuator on the transfer case is getting power. If you have the shifter on the floor, check to make sure the linkage is connected and properly shifting. Next, if the transfer case is working properly (you've done the checks) check the actuator on the front axle. Make sure everything is connected and working. Even if the transfercase is working, the front axle needs to hook up or you will not have 4wd.

There is a electric actuator in the front differential that needs 12v when 4wd is activated. If it has power then the actuator is bad. They are very common for failing