Ok I have a new to me 1999 Blazer. I got it ultra cheap due to it having been in a mild front end hit.

Previouse owner told me the 4x4 wasnt working but he had someone look at it and figuerd it was just the swich. I replaced that today and no luck, no change.

Switch will light up for a milli second when the truck fires but thats it. Buttons are non- responsive and I belive it's stuck in 4hi. I'm thinkin maybe the 4x4 control module?? But I have no experiance with computer controled 4x4's.

Anyhelp will be muchly appreciated.

 

did you check the vac actuator under the battery tray?
it may have been damaged in the accident?

 

Ahh so thats what that is... No it was not hit but i moved it when I pulled the rad support.
I'm thinkin it's probably electrical due to the switch not lighting when you press a button...But i'm probably wrong.

 

here check this out see if this helps ya

https://blazerforum.com/forum/tech-a...ill-help-7180/

 

The first thing I would do is check the TCCM for codes. See if it's trying to tell you whats wrong. The 4-button switch models (NV236) requires a full feature scan tool, but the 3-button switch models (NV233) can be done using a jumper wire at the DLC (process described in the Tech Article DIY section).

If there are no stored codes or you have successfully retrieved the codes, the next thing I would suggest is pulling the passenger side kick panel and having a look at the TCCM electrical connections. They like to corrode and cause all sorts of weird problems.

 

It's the 4 button model...So do I have to take it to a Chevy dealer to have it scanned or can any mechanic do it?

 

A mechanic with a good scan tool can access the TCCM. Depends on whether they know how though.

 

Ok had a friend scan it and coudnt get anything out of it...He pulled up a wiring diagram and found there was power going in but that was about it.
Pulled the TCCM to check for corrosion/dirty connections and it rattled when picking it up.
Sounds like something came loose in it. It's garbage...
Found a local parts truck close by and pulled the TCCM.
Parts numbers dont match but it's from a 99 with the 4 button switch.
From other websites looks like maybe they changed the part # durring the year with updated chipsets or something...

Old part # 1578800
new one #15154323

Hope this one works...I'll find out tomarow[trucks in the shop still]
At least the new/used one only cost me $20

 

good luck let us know what happens

 

Well finally got around to doing some more work on the truck...
Swapped the TCCM and scanned it again because I was still getting nothing. Scan came back with a couple codes and the guy who scanned it figured the encoder motor was toast to. Bought a used encoder and installed it.
Still nothing. Now im not sure what to do...dont want to keep throwing random parts at it..
Scanned it again a little while ago and heres what comes up.

co323-transfercase lock circuit low
co387-unable to complete shift.

need help...