Four wheel drive is not working

The way this works is the switch is turned and the GEM takes that request and engages the transfer case through the shift control module. Then it also tells the cluster that the switch state has changed.

However, we need to test what is coming out of the switch to start to find out where the issue is.

So I would go to the GEM module to start testing voltage. The GEM
on the Gray/Red wire sends power to the switch and then depending on the position of the switch it goes through a different size resistor and returns the voltage on the White/light blue wire.

So we need to go to the GEM and move the switch through the different positions and make sure the voltage changes. If it does not, then the switch is the issue. If it does, then we need to go to the Brown Pink wire of the GEM in pin 17 and find out if there is voltage coming out there. That is telling the shift module to engage the motor. If there is no voltage then the GEM is the issue. If it does then the shift module is the issue.

However, I suspect the switch or the GEM is the issue.

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

Let's run through this and go from there. Thanks

Yes it could be the t-case motor it could also be the gem module but not near as common. If you want to test it let me know and you will need a digital multi meter.

Ok first thing that needs to be done is make a fused jumper wire. Now you need to get to the GEM module (it is behind the radio). Now unplug it and put the jumper wire from pin 10 and ground turn on the key engine off and if the 4x4 light comes on the module is bad. Also measure for voltage between pin 14 and ground if voltage is present then you need to repair the gray wire from pin 14. Here is some pics the first is a pic of were the gem module is and the 4x4 relay which we will test next. The second pic is of the connector and the pin numbers. Let me know how it goes and we will go from there.

I need you to check if the actuator on the transfer case is getting power. Have a helper try switching to 4wd while you check for power. Please make sure the park brake is on.

Let me know what you find.

It can be cause by a couple things, vacuum to the front axle, or the electric actuator. IF the light isn't coming on, I would start by checking if there is power to the actuator on the transfer case. If there is, remove the actuator and check it for function.

Let me know what you find.

Joe

Good morning,

when you command 4 wheel low, does it feel like it is in 4 wheel low?

It is possible the actuator is bad on the transfer case but needs to be confirmed.

I attached possible issues but I need the code stored in the module to narrow the area of failure.

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

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Roy

Okay, got it. What tests have you done so far?

Again, do you have the code for the system?

I want to help but I need a starting place and the code will narrow the field of testing.

Roy

It does sound like your transfer case is the issue as it is most likely and internal failure.

Is the check engine light on and if it is, do you know the codes?

Roy

Start by checking Maxi-fuse #1, 4, 6 in the underhood power center, then check fuse #25, 26, 28, 9. If all good, remove the switch and using a test light verify power to the switch, and that the switch is passing the power through it when a differnet range is selected. This could be the electronic shift control module, the G.E.M. Module or the motor on the transfer case. You could also test for power at the motor on the t-case when differnet ranges are selected.

Check the wiring to the actuator on the transfer case. If it is clean and tight, check to see if there is power getting to it.

Let me know what you find.
Joe