97 Jimmy with patial 4x4 failure

I have a 97 Jimmy 4x4 with the 3-button 4x4. Real simple, I have 2 High and 4 Low but no 4 High.:shakehead A switch didn't fix it, niether did a module or encoder motor.:runaround: Where can I get the wiring diagram? Any tricks? Thanks so much.
Eric

When you initially turn the ignition to the RUN position, what lights come on, (2HI, 4HI, 4LO) and do they blink and have you tried to retrieve DTC's?

Turn the key on and all 3 lights come on for about 3/4 of a second, then go off. Got a code one time, for the encoder motor so changed it. No codes ever since then. Same symptoms. Push 4 Low it goes right in. 2 High and it goes right in. Push 4 High and you can hear see feel nothing and the front driveshaft still spins free.

It sounds like the 4HI command is not being received by the TCCM. A fairly common problem is corrosion buildup at the TCCM connectors. Carefully take the connectors apart: Check for corrosion and/or damage at each pin, pin socket, and also where the wires crimp to the terminals in the harness connector. The 4HI command is sent to the TCCM through the grey with black stripe wire, pay close attention to all connections, but especially to that one.

Sorry I've not been on for awhile, and thanx for the replies. I'm told the TCCM is the module behind the passenger side kick panel. I went there and not one wire ohms from the switch to that connector. I must have bad information; that must not be the TCCM because 4Low and 2 High work just fine. I'm trying to get my hands on a factory manual for the wiring diagram but no one seems to have one to sell.

The TCCM is located behind the passenger side kick panel:

http://kylestubbins.com/files/images/03_blazer_tccm_01c.jpg

There is a logic module built into the switch that sends the commands to the TCCM. You'll need to unplug the TCCM and the switch to check resistance on the wires.

So glad you're on! Hi I did indeed unplug both the TCCM connector (same place but different from the example photo; mine is bolted to the plastic kick panel itself, not the metal) and the switch. The wires don't show any continuity, (none of them) and the size and colors don't match either. I'm starting to think there is another module (the PCM?) or a connector in the loom somewhere that I don't know about.

At the switch, the brown wire should show battery voltage with ignition in RUN position. There is another connector between the switch and the TCCM in the dash however, the wire colors should remain the same from the switch to the TCCM. Something you can try is with the TCCM unplugged, pop the switch out of the dash, turn the ignition to the RUN position, hold the 4HI button and probe the wires on the back of the switch. The brown and the grey with black stripe should show battery voltage. Post your results.

The switch has B+ voltage at the "C" terminal wire, the red one. When held, the 4Hi switch sends power down the tan wire with the black stripe; at terminal position "D". All of our wire colors seem off. I have a 10/96 GMC Jimmy by the door sticker and the 10th V.I.N. character is a "V". Maybe someone has changed the harness or something. Can't even get a manual for this thing that matches. I'ma almost ready to take it to the sale! :runaround:

Hey look what I found! This seems to match my ride. TCCM behind center of dash!

http://www.autolib.diakom.ru/CAR/Chevrolet/1997/Blazer/SYSTEM%20WIRING%20DIAGRAMS/

Nice piece of detective work! With the ignition in the RUN position, when you select 4WD HI, does the grey with black stripe wire at the TCCM show battery voltage?

Sure does! I'm getting a module as soon as I can find one and see what happens. If I have to buy a new one, it'll be first of the week. Shootin' for tomorrow! All the wires from the TCCM ohm to the transfer case plug so I'm confident the module is the culprit. Not sure how to post that link hope everyone can read it that needs too. Let you all know how this turns out!

Makes a guy wonder, O'reilly's lists the kick panel module as the TCCM, but it sure ain't on my Jimmy. Wonder just what it is?

If you post what the wire colors are, I'll try to figure out what it is. Unless someone else knows and chimes in.

Well I looked inside my old TCCM and found there ain't much one can do inside there, (tiniest components I've ever seen) so I put it all back together and "Viola", I have 4Hi! It all works so gonna go with it for now. Must have been the dirty connection you mentioned, I sure didn't find any broken solder joints. The other module has a 24 pin connector in 2 rows of 12. Row A starts with 1&2 as black/white. 4 is yellow/black, 5 is light green, 9 & 10 are yellow and hot B+ KEY ON, and 12 is black/white.
Row B has 1 as brown, 2 pink; and hot key on, 5 is black/white, 8 is green, 9 is white, 10 is purple, and 11 is tan.