4x4 engage issue (not a vacuum issue)
 

- 1999 S-10 Blazer 4x4.
- Transfer case: 4 push button 4x4 "auto 4wd".
- 2wd works fine.
- Front axle vacuum actuator works very smooth and gets proper vacuum signal from the switch on the firewall.
- Front axle engages perfectly with the vacuum and cable.
- Front wheels "bind" on tight turns on gravel, excellent indication of front wheels locked.

Problem:
- No indicator lights on 4wd buttons
- Pressing buttons will cause proper "clicking noises" on the passenger kickpanel.
- I can put transfer case in 4low and 2high (no light indicators on buttons). I hear the encoder motor kick in. But truck will only spin rear wheels.

It appears that the transfer case is not locking in the front driveshaft.
I have disconnected the battery as well as pulled the 4x4 fuse & replaced - no change.

If this involves the TCCM, I need help on how to diagnose it.

Simple fix?

Thanks in advance!

When you pullxthe fuse wait one half hour put fuse back in. Turn key on no start. 5 times with buttons blinking each time or wait a few seconds before turning key off. This should reset everything. Worth a try

Fuse/Key thing did not work. Tried pulling battery again... nothing working.

No lights on push button dash piece.
Still hear encoder moving from 2wd to 4wd. Still will go into 4lo as well. Just no front driveshaft power.

Any other options?

Assuming you have the NV236 Transfer Case, this Tech Article might help: https://blazerforum.com/forum/tech-a...rmation-41198/

It appears I am not getting reasonable voltage to the green LED indicator bulbs on the 4 button controller to both 2wdhi and 4wdhi. I am getting the white background lighting on the buttons.
I am getting 0.08volts... but nowhere near 12.0

TCCM plugs look clean. Only 1 pin on the TCCM was very lightly corroded. Cleaned and put back together.

No change.

Anyone thinking TCCM?

Update:

Not sure if there are anybody here that knows about these 4x4s - with the lack of responses?

Anyway.. Replaced 4 button 4x4 switch. Now I have lights.

1. 2wd works fine.
2. Pressing 4hi or Auto4wd results in the 4wd light blinking, but no engagement
3. Pressing 4lo results in the truck going into 4lo, but the light stays blinking. (the truck does not lock the front axle to the T-case)
4. Vacuum actuator works fine. It locks the front 2 wheels together.
5. No "power" from the T-case to the front axle.
6. Pressing buttons between 2wd and 4hi results in clicking on TCCM
7. Pressing buttons from 2wd to 4lo results in clicking at TCCM and clunking from encoder motor under the truck.
8. TCCM connectors are clean.

Help??

Did you go to DIY Tech artical. Lots of info there on the subject.

Can't find any answers.

I must have a unique issue?
Funny thing is, the neighbor has the exact same issue.

My 01 is stuck in 4low right now and will not do anything but stay there. Has not been on the road in about 3 years and when I first got it going it was in 2 hi. Relaced all vacuum lines while I was working on it so after head gasket decided to see if the 4 wheel drive would work. No lights most of the time. Seldom hear anything. Doing fuse test now. It's in 4 low for sure but I really don't know if the front wheels are locked. Could be we have the same issue.

My 96 Blazer does not engage either But I can hear it clicking as though it is engaged from under the vehicle . 4wd low light comes on just nothing to the front wheels . Tired Of Snow and being stuck in a 4WD that doesn't work .