Won't go into 4wd

Hi my 2001 Jimmy 2dr with AUTO 4wd won't go in to 4wd mode, last night it was raining really heavy so I attempted to to into AUTO 4WD mode the light on the button blinked for about a minute then it kicked back to 2wd mode. I tried at different speeds and even stopped in nuteral, I also tried backing up under power and coasting , also tried rolling fwd coasting still no help , I tried 4wd high, didn't work and I tried 4wd lo, still no joy.
any ideas?[COLOR=blue][COLOR=blue][FONT=comic sans ms]

You'll need to get some codes read, but in my experience with the symptoms you described, you'll need a new encoder motor.

Don't start replacing anything just yet, find out any codes that exist and let us know.

Hope we can help.

I just had this problem a few months ago. It turned out to be a blown fuse. I replaced the fuse and all works fine now. I couldn't find a reason for the fuse to blow so I'm not sure what was the real problem.

Thanks I,ll Check the fuses tomarrow,
I had the codes read it showed: no faults/no codes?
all input is greatly appreatied.
Thanks, Sean

You need to have the TCCM codes read, not the PCM. On some vehicles you could ground one wire at the DLC and watch the 4x4 button lights blink for the code but I don't know if thats possible on the new ones

OK I checked the fuses all are good, I even swapped out the 4wd fuse with the spare to be sure still no 4wd.
Does anybody know for sure how to read the TCCM on a 2001 jimmy? I don't want to jumper computer terminals with out some guidince.
Thanks. Sean

Check Vac On Bubble On Inside Of Hood Samething Happened Here

Please explain "bubble inside of hood"
Thanks, Sean.

Might check the fluid level in the transfer case. Remember, if you need to add fluid the newer cases Do Not use ATF. Most of them use a GM only fluid.
Also check for any loose connections to the actuator motor on the front axle and to the transfer case shifting motor.
When you push a 4WD button do you hear any noise like something might be trying to work?
Just some simple things you might check before going to the shop. Not that the shop is a bad place to go. It's just a little embarrassing to find out the problem is only a loose wire.
:dupe:

Yea, I tried all the easy stuff but I still need info on how to read the tccm codes, also I don't have a TCCM fuse only a 4wd fuse.
Thanks, Sean

I still need a procedur for checking the TCCM codes.

I don’t know how to get the codes from the VCM (Vehicle Control Module) without the dealer’s Tech 2 tool. (Sorry)
However, I have a 2000 Silverado with the Auto-4WD. I started getting the “Check 4WD” message and it wouldn’t shift into 4WD. I was told that I needed a new switch, can we say lots of money? :mad:
What I found was I could remove the switch and open it with little effort. I then started checking the circuit board inside the switch. What I found with a magnifying class was that there were cold solder joints at all of the pins for one of the wiring harness plugs. I took a solder gun and made the repair. Been working great ever since.

Cost:

New Switch: $0
Labor: $0 (except for the Beer).
Working 4WD: Priceless.