Service 4wd display & multiple stored codes

[Lindsay007s]

About a week ago I had a completely unrelated issue with my (pretty much) stock '03 Z71 Tahoe, which lead me to having the codes run. No active codes but several drivetrain codes were stored: C0306, C0321, C0327, C0374 and C0379. Since I hadn't had any related issues I assumed they were never cleared from something maybe a previos owner had to deal with. But like a good little OCD girl I wrote them down, cuz ya just never now.
Well, today on my way home from work (exactly a 5 mile trip) SERVICE 4WD showed up on my message center/odometer. So, out of curiosity I pushed the auto 4wd selector and nothing! Didn't even blink! I've used 4hi maybe 3x on the beach and used auto only last winter when we had a lot of snow. A couple of times in the distant past the red neutral light would be on when started and put into gear (drove fine though), I would turn the truck off and restart and it would be fine. That worried me at first but then didn't do it again so I forgot about it.
I have looked up all the stored codes individually but am wondering what it means to have all of them present together, along with the service 4wd display. Surely someone has seen this before?
Sorry to be so long winded but I have done some searching and I'm just not making the connection that everything leads back to 1 problem.
Maybe it's a top secret self destruct sequence triggered when 140k miles are turned over? Hahahahaha! Seriously though, thanks in advance for any advice!
Add: it also has 2 codes that I didn't look up previously because they were of a different series: B2725 (4wd switch) & U1220 (cannot find any info). Maybe the switch/selector is the problem? Hopefully...?

 

[4WDTRK]

Generally speaking this is the transfer case encoder motor going bad. When the motor goes it bad it starts to feed resistance back to the switch and causes things to go haywire. Worst case it can potentially shift into 4WD low at a really bad time (i.e. freeway speeds) and cause big damage to the transfer case. That's where I would start.

 

[jose6326]

Not sure if you fixed any of your 4x4 issues but this might help

I got the same service 4x4 message and the dtc B2725

Since i fix flat screen tvs i decided to take apart the switch Instead of buying a new one

The solder points on the circuit board for the pins that connect to the connector or wire harness had hairline cracks. I needed a magnifying glass to see it.
I found 3 solder points were bad which cause resistance which in turn causes the dtc B2725 to come up

I resoldered all the solder points not just the 3 and now the code is gone and my 4x4 functions right on time for the snow storm

Don't mind the broken bulb it was already burned out lol
Yes it is a ****** solder job but I did it fast to check if that was the issue lol

 

[SLCHOE]

Generally speaking this is the transfer case encoder motor going bad. When the motor goes it bad it starts to feed resistance back to the switch and causes things to go haywire. Worst case it can potentially shift into 4WD low at a really bad time (i.e. freeway speeds) and cause big damage to the transfer case. That's where I would start.

What?

No.

Dorman 600-120 is all you need.

http://www.dormanproducts.com/itemdetail.aspx?ProductID=45401&SEName=600-120 (autozone carries dorman parts)

The tranfer case encoder motor has a position sensor to tell the PCM where it is engaged. When the sensor goes bad as they very commonly do, the switches start to do weird things. Not responding, not lighting up at all , lighting up in neutral only, really the whole gamut of possibilities. For instance I was driving down the highway at 75 mph when the light lit up for "4 LO". Obviosly, doing 70 mph I was not in 4 lo.

Usually if you take this to a shop they will charge you about $800 parts and labor to change out the encoder motor for the transfer-case.

In actuality the motor itself is perfectly fine. That is what costs so much. The position sensor inside the motor is what really is the faulty components and is cheap to fix.

http://www.fullsizechevy.com/forum/...-encoder-motor-sensor-replacement-w-pics.html