On an 2001 Blazer ZR2.
Since I've been having problems with my 4WD,something has been draining my battery. 2 y/o battery died. Voltage reg. outputs over 14V.
Last week, I bought a brand new battery. Parked the truck Friday, went out today, and the battery is completely drained.

I disconnected the TCCM today, and noticed I had 12 volts on the orn power wire with ignition off. Also notices I had 14.5V with engine running.

Is the TCCM draining it?

4WD problems, which started the same time the 2 y/o battery started to drain.

from a week ago: Haven't looked at the TCCM yet, but it does click when I select the different buttons. The truck is stuck in 4WD Hi right now. 2 y/o battery died today, don't know if it's related to these 4WD problems, or just a bad battery. (My luck sux).

So anyway, I put a new battery in tonight. Took the tray out, and noticed the actuator was engaged. Disconnected the vacuum to release the cable. Cable moves freely. So put the battery in, and it's still stuck in 4WD Hi. switch to 2WD and the light flashes, TCCM clicks, then light switches back to 4WD Hi. Trieid switching between 2WD, 4WD Hi and Lo, and 4WD Auto. All positions reset back to 4WD Hi.
Maybe tomorrow I'll drop the panel under the glove box and find the TCCM.
I am not optomistic.
Never heard a peep out of the TC Motor, so I'm starting to suspect the motor. No code light right now, so maybe it'll show up tomorrow. I'm probably going to take it in, as my cheapo scanner is just that; only good for SES trouble shooting.
Last Weekend:

Checked actuator under the tray agian.
With engine running, I disconnect vacuum, watch the cable release (about 3/4 to 1" travel), tried switching to 2WD - light blinks, then goes to 4WD hi and stays blinking. Still won't go into 2WD. Buttoned everything back up so I could move the truck slowly while switching, still no luck.

2 weeks ago I had 4WD Hi and Lo. It won't go into 4 WD LO or 2WD. Today with the 4WD Hi light on, I only have rear wheels turning, even though the cable is actuated (pulled out).

Can the encoder motor being stuck/dead cause this?
I don't want to chance replacing it (NP8 setup) as it's rather pricey for a rebuilt ($250.00)

Also of note, I have the older (original) TCCM, #15748800. GM no longer makes this, and it's superceded by 12577412.

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The orange wire comes from the ATC fuse which is a 'hot at all times' wire meaning that it is intended to be supplied with direct battery power.

On the battery drain, you really need to just dig in and find the circuit responsible.

On your 4wd problems, you need to test the switch in the dash and check all of the connections for corrosion.

 

Well, I figured it out last Tuesday.
I had replaced the alternator around the 1st of Jan. Bearing were noisy, so I figured time to replace it anyway. Still didn't have 4wd working properly.
All of a sudden 1 week later, my battery drain is back. Disconnected the TCCM computer for a week, battery drain goes away. Everytime I plug the computer back in, or disconnect and reconnect the battery, I hear the TCmotor run for about 3 seconds. It's either the computer or Motor. Pushing buttons caused relays to click in the computer, and I could hear the motor running with the button pushes. Switch must be OK.
Finally had a day nice enough (warm ~30 degrees) to crawl underneath and take the TCMotor off. The motor would run when I pushed buttons, but nothing would change on the Transfer case. button stuck on 4WD high, but truck is in 2WD. Front shaft from TC to front hub is locked, so I know vacuum is good and front shafts are locked.
Dropped the TCMotor, and noticed I could turn the slotted receptacle for the TC shaft by hand. Not good.
Ordered a new motor Wednesday, got it today and put it in (came from PA., got stranded by the East Coast storm). Had to turn the TC shaft slightly to get it in neutral. buttoned everything up, and it works. Took 5-10 button pushes from 4H to 4L to 4A to 2W before it finally shifted out of neutral. Had me worried for a bit, thought I'd have to take the motor off and shift the TC by hand.
So,apparently the old TC motor gearing is stripped. I can turn the fitting with my pinky (and I'm getting weaker the older I get) Apparently, the motor must have been running continuously, in order to drain the battery if it sat more than a day.