Blaze-

From what I've read, lots of us with this year(ish) model are having similar problems.

I'd be very interested to hear what your new mechanics have to say. Please do let me know after you've had a chance to talk with them.

In the meantime, can you fill in a few details so that we might get closer to a *final* solution?
1) Have you gotten DTC code(s)? If not, try grounding the #13 pin on the OBD computer connector under the driver side dash. The #13 pin is the fourth from the right on the bottom of the connector (you can jumper it to #5 or ground it to the parking brake lever). After grounding, turn the ignition to the "ON" position without starting the vehicle and count the number of blinks on the 4WD push button dash control. I got a DTC code 2, indicating a miscommunication/malfunction with the encoder motor.

2) After that step, try clearing stored codes in the TCCM by removing the #8 fuse in the instrument panel fuse box for a minute or so (it's marked "CTSY LP" and is a 10 amp fuse). After a couple minutes, replace it, then turn the key to the "ON" position without starting five times. This should clear stored codes and, at least in my case, returned full function to the 4WD system--at least for awhile (I know there's a specific number of failures before the TCCM reverts back to 2HI/4LO only as a safety precaution, but this seems sporadic). It would be interesting to know whether this works for you and if so for how long.

Please report back if you have a chance to try this (it's easy and only takes a few minutes).

 

I have not gotten any codes. The original place could not get into the system deep enough. I am basically starting from scratch. Which might be good. At the time they were changing encoder motors and TCCMs the transfer case was dying, so there might have been too much going on. Thank you for the info., at least now I have that. I will let you know of my findings, it will probably just take a while. I just got the Blazer inspected and had to work on it for that and did some might as wells, so I'm laying off of it for a while. Between me and these guys things actually got fixed, so that's why I am putting faith in them. And as I said before, I am going to try one more time and then it is Ghetto 4x4 time.

 

Just a thought...if you DO end up changing the TCCM, there were a couple of revisions to the unit in later versions. I don't recall the number for the latest revision, but it should be easy to find in any parts store listing.

 

I am having similar problems with our 99 ls but here is the strange part....there is no wire in pin 13 or a orange wire in the loom!. I have been a ASE tech fo 25 years and never seen that. Any ideas(cant find anything in alldata)

 

I had TC shifting issues, no 4x4 hi, check out my fix from last September... still working fine....

https://blazerforum.com/forum/2nd-ge...-repair-81850/