Since you're in the buying mood, I'd recommend going to alldata.com and buying a DIY subscription for your specific truck. I think it's less than $30 for an annual subscription and you will get the Technical Service Manual, all TSB's, color wire diagrams, etc.

EDIT: I know this is going to sound silly, but sometimes it's the little things...when you're trying to shift it out of 4LO you do have transmission in NEUTRAL, yes? Not PARK.

 

Yes, as indicated by the dash, I only attempt engaging or disengaging the 4x4 system while in neutral.


I'll take a look at alldata - I've got the Hanes service manual book, though it's proven kinda worthless tbh... what's another 30$ on 17k?

 

Haynes is a gnat on on Alldata's butt. Do you have a DVOM and are comfortable with it's use?

 

Yes, and while I wasn't before- after my Last thread I picked up a few things.

 

For future reference, don't test the encoder motor when not mounted in the vehicle, you can damage it. Have you checked the 20a ATC fuse in the Underhood Bussed Electrical Center (UBEC)?

Starting at the Transfer Case Shift Control Module (TCSCM) (behind passenger side kick panel) and assuming your familiar with backprobing connectors (maybe I shouldn't assume) while components remain connected.

Access the TCSCM behind kick panel and not disconnecting anything. Best to backprobe with a T-pin, but even a straight pin will work, just insure as you probe the back of the connector you are not letting it touch other wires, pins, or metal in general. You aren't poking the wires but probing into the back of the connector. Backprobe the ORG wire on C2. DVOM black lead connected to good ground. I'd recommend running a wire to the B(-) post of the battery since this may help identify bad grounds all the way back to the battery. Red lead connected to the T-pin. Key On Engine Off (KOEO), you should see B(+) voltage (~12v).

Key OFF while you set up for next test.

Backprobe LT BLU wire on C1 pin F14. NOTE: There are a couple LT BLU wires. The one you want is next to two LT GRN/BLK wires. It's best if you look at a pinout diagram to be sure you are on the correct LT BLU wire.

Still connected to good ground, red lead on T-pin, KOEO, you should see these voltages +/- 10% as you push each button on the transfer case selector switch:Correction: Voltages originally provided to OP (in red) in correct order from source. Based on OP voltage measurements and a secondary source, I have listed (in green) the voltages correctly listed for anyone that may later come upon this thread (voltages are (+/-)10%).

Correction: Voltages originally provided to OP (in red) wer NOT in correct order from source. Based on OP voltage measurements and a secondary source, I have listed (in green) the voltages correctly listed for anyone that may later come upon this thread (voltages are (+/-)10%).
No button pushed 0.79v
A4WD 3.18v
4HI 7.52v
2HI 4.81v
4LO 2.39v
Neutral 3.59v

No button pushed: 0.79v
A4WD: 7.52v
4HI: 4.81v
2HI: 3.18v
4LO: 2.39v

If this test passes, indicates selector switch and wiring to TCSCM from switch is fine.

If this test does not pass, remove and access the back of the selector switch (leaving it connected) backprobe​ the LT BLU wire​​​​​​ on the squarish 8-wire connector, KOEO, test for same voltages.

Let us know where you are after that. If I'm not available, there are others that can jump in and take it from there.

P.S. Record steps you take and any measurements on a piece of paper or a notebook. Not only can it help us along the way if we need, but it can help you to look back...you'd be surprised how useful it is to do that.

EDIT: Please note I mistakenly stated "starting at the switch" I meant to state "starting at the TCSCM". Changed it

 

Alrighty, finally got a chance to pluck away at this some more - haven't picked up another TCCM or dash switch yet. Still gotta dig around for a scan tool that'll let me send commands to the TCCM. But I was able to hook up a wire straight to the ground on the battery and run it into the cab with me for testing.

without further ado, my results.
Backprobe of ORG wire on C2 while KOEO reads12v
Backprobe of the LT BLU wire on C1 pin F14 reads as follows

No button pushed 0.79v - reads good at 0.93
A4WD 3.18v - reads double at 7.5
4HI 7.52v - reads 4.9
2HI 4.81v - reads 3.2
4LO 2.39v - reads 2.5
Neutral 3.59v - this means push 2hi + 4 low right? Reads 4.1v

Moving onto probing blue wire attached to selector switch, got identical readings.

No button pushed 0.79v - reads 0.93
A4WD 3.18v - reads 7.5v
4HI 7.52v - reads 4.9v
2HI 4.81v - reads 3.29
4LO 2.39v - reads 2.5v
Neutral 3.59v - reads 4.1v

Where does this lead me next for further testing?

 

It looks like the selector switch could be bad. Especially, the A4WD button. There is an 8 volt reference going to the switch and it appears the resistor on that button is shot. But to verify, I would disconnect the switch from the harness and using an ohm meter on pins "A" and "B" check the resistance of each button as they are pushed. Compare to the resistance values LesMyer listed in that link I posted.

 

"The resistance between connector 1 pins A & B are as follows for single button push:No buttons pushed - 9.09kOhm (9090 Ohm)4Low pushed - 2.345kOhm (2345 Ohm)2High pushed - 1.516kOhm (1516 Ohm)4High pushed - 0.663kOhm (663 Ohm)
Auto4WD pushed - 0.064kOhm (064 Ohm)
You are looking for the pins that connect to the light blue wire (Pin B in connector 1) and the light green with black tracer (Pin A in connector)"

I'm assuming he is talking about the 8 Pin connector on the back of the selector switch? The vaules I got dont exactly look close to what is listed. I get a reading of 0.836kohm that goes up or down 20ohms at most when pushing the buttons.

Picked up another selector switch from the junkyard, forgot to grab the TCCM, swapping the switches out didn't resolve the issue, but I'm suspicious of the switch cause it's leds where pretty faded - gonna take the junkyard one apart and reflow the board solder in the oven and see if that revitalizes it.

 

Correct, ohm meter leads connected to pins on selector switch that mate to LT BLU and LT GRN/BLK wires on C1. The range I have for each button push are:

A4wd: 61.7 - 68.1 ohms
4HI: 656 - 670 ohms
2HI: 1.50k - 1.53k ohms
4LO: 2.32k - 2.37k ohms
Neutral: 1015 - 1035 ohms

You're measuring the switch itself with it disconnected. One lead on pin "A", the other on pin "B" Not to sound insulting (but sometimes I assume and don't state what I think is obvious and find out I should have stated).

I've reflowed solder on 3-button switches, due to the fact they can crack, and it is a fix. Have not run into one on 4-button so I can't say if that is also a problem with them. I re-flow with soldering iron. Have to say I've never re-flowed/soldered a component by throwing it in the oven. I would think throwing it in the oven to reach temperature to reflow could damage the component in another way.

 

"You're measuring the switch itself with it disconnected" LOL! Ooops, yeah that was definitely the little detail I was missing.

Good to hear you've gotten success out of reflowing the 3 button switch, gives me hope it'll work.


As for the oven re-flow technique; it's a flash fry not a slow cook. Solder melts almost instantly, so 10-20 sec in the oven at 550f has gotten great results for me over the years on alot of consumer electronics.