2002 Blazer Won't shift OUT of 4WD?

[Brokecelebrity]

I seem to have a problem getting our 2002 Chevy Blazer to shift out of 4WD.
We hardly ever use the 4wd, but quite a bit of snow today, so switched it on.
Later in the day, it started to melt and we had dry pavement, so we tried to switch it back to the 2HI position.
After pressing the 2HI button, there were several clicks, sounding like it was coming from the glove compartment area, the 2HI light would flash for a couple seconds, then switch back to 4HI.
It is an automatic, I searched the manual and tried everything it suggested, I'm thinking maybe some type of relay, sensor or fuse is out?
Any suggestions appreciated.

[FishFind]

check the accuiator. It is a rubber boot under the battery. they tend to tear and if they do it is stuck where it is at. It is controlled by a vacuum.

Try and put car in neutral and switch it.

If you where in 4lo and attempting to go to 4hi or 2 hi the car must be going less then 5mph or in neutral to switch.

Keep us posted.

[Brokecelebrity]

Thanks for the tip.
I ran all the leads I could using the forum and the manual, ran out of ideas, so I took it into the dealers for a "$32.50" diagnostic.
They called me while I was at work, said the codes showed it was the TCE and the TCCM were toast and needed replacing.
Price that was quoted for parts and labor was on the high end of $800!
I told them I'd think about it and be in after work to pick it up.
I wasn't about to pay them that much, if I know what the problem is, I can usually do it myself, I figured for $32 to have the diagnostic run, it would lead me where I needed to go in order to repair it myself.
Long story short, I picked it up after work, the price was now $65, it magically doubled sometime between the first quote and when I picked it up.
I know what dealer I WON'T be going to anymore.
I'll get on line and see what Napa charges for the parts and go from there.

[FishFind]

I doubt that is what is wrong with it but if it is start with the tccm. it is located behind the glove box and you can get them for about 25-50 bucks on ebay.

The encoder motor is $100-$300. I doubt that is what is wrong with it though. I would check 3 things first.

1- check the actuator. it is under the battery support pan. They tear easy, especially if you don't use it much. it is a $30 dollar part.

2- Check the vacuum lines going to the actuator. Its just a rubber hose and they dryrot.
2hi 4hi and 4lo are all controlled by that hose and actuator. If it has a tear or crack it will attemt to switch to or from what ever you select but wont be able to make a vacuum and pull the actuator.

3- the 2hi,4hi and 4lo selection switch. they can go bad as well but if you hear a click I would guess it is good.

Here is a pic of the actuator http://www.autozone.com/autozone/par...mString=search

Also first if you think it is the encoder motor try to unplug the harness and plug it back in first. it is located on the transfer case drivers side.

[FishFind]

off the site with the pic of the actuator "The 4WD actuator engages the vehicle s 4WD.
When not replaced, vehicle will either be unable to lock or unlock the 4-wheel drive."

[Brokecelebrity]

Thanks for the information.
I was talking to a friend today about it, he has a 2005 Chevy truck, same chasis and transmission, and he said his was also stuck in 4wd since a couple days back. The vehicle he has only has 98k on it, maybe a design problem with the model.

[Brokecelebrity]

Updated:
Now won't go into reverse!
I found a local shop that did a diagnostic on it.
According to them, the transfer encoder was good, it was the TCCM module that was toast.
There are three versions of this for the Blazers, he ordered the 7 pin unit and schedule us for a repair.
I dropped it off yesterday before work, asked him if it would be done today, he said it should and I would be able to pick it up after 5 o'clock.
I got off work, walked down to the shop, it turns out his supplier had sent the wrong unit, they discovered this AFTER they had the truck up on the ramp and taken apart.
He said once they discovered they had the wrong unit, they bolted everything up again, took it down, called their supplier and explained the issue with them, and said once they had the right unit, they'd fit us in for the repair.
I backed it out of the parking lot, drove home with one stop at the store, got home, tried to reverse it into the driveway, all I got is whining in the rear and no movement. I put it into drive, headed up the block, turned around and nosed it into the driveway. I tried again to put it into reverse, same sound, whining or whirring, you can hear everything turning, but it's not engaging.
It COULD be a coincidence that the reverse went out right after the TCCM did, but what are the odds?
Any way the shop could have missed hooking up an electrical connector or vacuum line that would cause this?
The truck only has 81k on original transmission.
Any info appreciated.