Hello and welcome to JustAnswer!
The first thing you will want to do if the switch won't even light up is check fuses. Fuse 9 and 11 in the fuse box in the dash both are for the transfer case switch. Also check fuse A in the power distribution center. This is a power feed for the transfer case module.
You may have a deeper problem with wiring, the switch, module, or the transfer case shift motor, but checking these fuses is definitely the place to start. Full diagnostics of this system would require a scan tool to access the module and see if it's awake and storing fault codes and to check the switch and shift motor operation.
Do you have a voltmeter to do some electrical testing?
Pull the transfer case switch out and unplug it.
Put the black lead of your meter on a good ground and leave it there for all testing. Use the red lead of your meter to probe the following wires:
Then flip the meter over to 200 ohms, probe the solid black wire.
Let me know what voltage you see on the first three wires and the resistance to ground you see on the black wire.
Yes, the transfer case switch on the dash. All you need to do is turn the key on, you won't need to start the engine.
Okay. little bit of a pain to get to the switch.
DarkBlue/white was dynamic. would start around 40mv and climb to around 168-200 and then restart. This was the same for for the yellow/Lblue and orange wire.
The black wire seems completely open. with 10 Mohms
Hope this means something.
Are you sure this meter is ok and was hooked up properly? If these results are reliable then you have at least 4 different problems.
Go out to the battery and put the black lead on ground, red lead on positive. Set the meter to 20v DC and read the voltage.
Then set the meter to 200 ohms, touch the ends of the test leads together and make sure you see 0 ohms.
Put the black lead of the meter on a good unpainted grounded piece of metal under the dash. Probe something with the red lead that you are sure has power. Turn the key on, use something like the very center inside the lighter/power outlet. With the meter set to 20v DC you should see battery voltage on the meter.
Once you are positive the meter is set up correctly and working right then go back and recheck these wires again. With the results you first had they show you have no ground, no power feed from two fuses, and no 5v reference to the switch from the transfer case module.
Looks like I picked a bad grounding point.
Looking deeper, the orange wire is for the illumination, this wire won't have power unless you turn the park lamps on. We're ok there.
We've got power to the switch from the fuse. We've also go ground to the switch. What we're missing is the 5v reference from the transfer case module. We need to next see if it's getting it's powers and grounds.
Access and unplug the transfer case module under the dash. Remove the trim panel under the steering column and you'll find the module mounted in the dash just to the right of this opening. Unplug the connector and check for ground on the two solid black wires. You should see battery voltage on the light blue/red wire.
The bus communication wire is the violet/yellow wire. This one should show something under a volt with the key on and slightly fluctuating.
I believe the blue module you found is what you are looking for.
turning out to be one hell of a project.
Been trying to get to the connections of the blue module this whole time. There are two separate connections of wire going into it. is this the right module. You didnt mention two connections and before I take anything else apart I want to check.
There should be three connectors. There will be one 4-way black connector, one 16-way gray connector, and one 16-way black connector.
Once I got it out I saw the third connector.
Both Black wires had 0 ohms.
Violet/yellow Did hit 1.4v but mainly stays below 1v
Must say they dont make it easy to get to these things. Guess thats why the Pros exist.
It sounds like you've got everything the module needs to work but it won't. The central timer module sends a signal to the transfer case module over the PCI network to wake it up. Since the bus wire voltage looked normal we know it's able to communicate over the network.
The grounds checked out, and so did the power feed. The transfer case module has everything it needs to work but won't power up, so it sounds like you are going to need to replace the module.
Before replacing the module, if you are having any other electrical problems let me know. If you are having problems with interior and exterior lighting and intermittent wipers it could be related to this.
Unfortunately I don't have access to a full parts catalog at the moment. I checked both of the sources that I do have and couldn't come up with a price or part number. It's not terribly expensive.
It's not a real common part to replace, but they do fail once in a while.