Hey y'all, I know there's a bunch of posts covering 4x4 issues but they all seem like they go off topic and it kind of just ends up being a slew of information so I'm sorry if this is repetitive... Anyways I have a 99 blazer with the 3 button switch that the 4x4 recently went out on. Redid all vacuum lines and replaced switch.. symptoms right now are flashing of lights when trying to engage in 4hi/lo as well as the TCCM clicking and then just resetting to 2wd... After a couple times the lights stop flashing at all until I unplug TCCM and then it just goes into the same symptoms I listed previously.. I did the little test at the OB2 by grounding the port and I come up with 3 flashes but can't figure out what this actually means.. any feedback would be appreciated, this is starting to get aggravating. Thank you guys!!!

 

A not uncommon failure point is the TCCM. The clicking you hear are the relays on the circuit board. They should not repeatedly click. If they are, the TCCM us likely bad.

It sounds like you are familiar with getting access to the TCCM. Have you visually inspected the electrical connections to it? I have heard of these becoming corroded and giving them a clean helping.

 

Yeah I've checked the connection on both sides and it looks clean/no pins missing etc, it only clicks once while the lights on the switch are flashing and then it resets to 2wd

 

Ok, so no repetitive clicking? Then the TCCM might be fine.

 

Check out South Main Auto on YouTube he has a few S-10 trouble shoot clips Mr.O is very helpful.