Howdy, new to blazers and new to this forum, I have an 04 blazer with the three button 4x4 that I’m at a loss on how to make it work. So the issue I’m having is with the electrical portion of the 4x4, the switch, tccm, and transfer case motor have all been replaced. Yet when I press the button it blinks a few times, the tccm clicks then it returns to 2wd. If anyone has had this issue or has knowledge on how to resolve it I would greatly appreciate any help.

 

Was the TCCM replaced with a new one?

Have you checked the vacuum lines to the transfer case and to the actuator under thr battery?

 

yeah it was a brand new tccm, since it functioned the same as the one I replaced I ended up returning it. I haven’t messed with the actuator under the battery tray, because the few times I got it to go in 4x4 the axle engaged properly. That lead me to believe the vacuum lines and actuator under the battery tray were functioning.

 

About the only thing I can think to try is to double check the quality of the electrical contacts in the connector to the TCCM as these have been known to corrode. Although, I'd be surprised as you have obviously disconnected and reconnected it several times.

You might check for vacuum leaks as the actuation of the 3-button transfer case is at least partly through vacuum. I have a 4-button t-case so I have no direct experience with this.

Hopefully someone else can help out.

 

Thank you, ill definitely check that out this weekend, I got a new vacuum switch for the transfer case just to try it. I will get back on the forum and post my discovery when i finally solve the issue, mine can't be the only one with this issue.

 

Another common problem is the solder joints on the electrical connector for the 4x4 switches; in your case the 3-button switches. Just need to remove the 4x4 buttons, separate the case to access the circuit board, then reflow/re-solder the connector pins in the circuit board.
Although I do not think this is your solution, as the TCCM is responding, but it is a quick, $0 cost to try, if you can solder.
Check all vacuum lines under the hood, left side, about where the brake booster is. Very common for these lines to rot. If the lines are soft or gummy, replace all of them. Just get about 8' of hose from auto parts store and replace one at a time.
Good luck.

 

Here's some info on your 4WD system.

https://blazerforum.com/forum/2nd-ge...-blazer-89670/

Since light blinks, transfer case is supposed to be moving to another position. So voltage should be going to the motor on the transfer case while the light is blinking. This can be checked using a Digital Volt-ohm meter in volts mode at the TCCM with the TCCM still plugged in to the wiring harness. Probe across C16 (black) and D1 (red) with the two leads of the meter. If the system is trying to change the position of the transfer case, there should be 12V (or negative 12V, depending on direction) across this while the light is blinking.

No Voltage = then it is the controls (fuses, wiring, TCCM, selection switches)
If Voltage = then it is TCCM motor or transfer case.

Good luck

 

Double check the vacuum line, I had a will she/won't she engage problem with mine where i could hear it engage in 4-low. The ratio would change but the front wheels would not engage, vacuum actuator tested fine but LannyL81 said, the lines were old and soft. While replacing some other vacuum lines, I found two hoses were spongy with small burn through spots so I went on the hunt for more. After replacement, 100% activation within a few seconds between 2HI/4HI/4LO (and in my case a 4 button, automatic AWD). It's amazing how interconnected some of the systems are on these trucks, sometimes in counter intuitive ways.