99 blazer zr2

After a quicky search i did find a few things that could lead me in the right direction. Also after lookin all over the web..

here are my symptoms: Drives and runs fine, no lights, no nothing on the dash. The 4x4 switch on the dash and is a 3 button. The lights on the buttons work. When i go to switch for 4hi or 4lo i hear the TCCM click, the lights sometimes flash for a few seconds, sometimes not. But no actual 4x4 stuff happens. ( Im pretty ignorant with 4x4 stuff.. first one) Now i read somewhere something about if thats happening to check the encoder motor? Is that the 4x4 actuator motor? Because i do not hear that doing anything.

Just got back from a parts yard with a "new" TCCM and it did the same thing. I pulled it off and put the original back on since it had no effect.

This is what i found from another not to be named site..

"If you can hear the encoder motor working and get flashing lights I would check the actuator, I do believe on a 1999 it has a sensor that detects when the actuator is pulled in when trying to engage 4x4, when the signal from that sensor is made you will get a steady light on the 4x4 switch, if it is not made but the encoder has engaged then the light will flash letting you know you have a problem.

The whole system is pretty simple, If you can hear the encoder motor working check that off the list, you replaced the switch so check that off the list. Now move on to the actuator, pull the vacuum hose going to the actuator and have someone shift it into 4x4 and see if it is pulling vacuum at the end of the hose, if you have vacuum jack the front tires off the ground and manually pull in the actuator and see if the front axle engages, if it does then you have a bad actuator, if it does not you have either a broken/stretched cable or something wrong in the axle such as the shift fork (Highly unlikely)!

If when you check for vacuum at the end of the hose going to the actuator and you have no vacuum then the transfercase vacuum switch is bad, it is located on the side of the T-case and has 3 vacuum lines coming out of it, one of those lines is nothing more than a vent line and it is not uncommon for it to suck some **** into it making it not work anymore.

I highly doubt it is a tccm, 99.99% of the time when 4x4 dont engage it is either the encoder motor, T-case vacuum switch, actuator, 4x4 switch, vacuum hose from switch to actuator, stretched/broken cable...these are all common problems!"

My mechanical skills are pretty good so i feel i can tackle the problem at hand if i had an idea where to start. I mean ive rebuilt a few engines and trannies, im no idiot with the other stuff. Help a 4x4 newb out??

P.S. sorry if this have been covered and then covered again. point me in the right direction if it has been.

 

Did a little more looking. Found this.. https://blazerforum.com/forum/tech-a...ill-help-7180/

Will try some of these. Seems like im not getting vaccum to somewhere via a leak somewhere. I have some strange things going on with my blend door as well for my HVAC. So my assumption is that these things are related. I just put a CAI on my blazer. would that have any kind of effect?

 

How are the HVAC controls, all working properly? As in you turn it to defrost & it blows out the defrost, same for floor or vent. They all work as they should?
Sounds like a vacuum issue. It may have enough vacuum to start to activate the 4wd actuator at times & other times not enough.
Try reading through this Search I made. Lots of similiar issues.
Blazer Forum - Chevy Blazer Forums - Search Results

<edit> So I was doing that search for you while you were posting the 2nd lol.
CAI shouldn't effect the vacuum unless you bumped a vacuum line installing the CAI. There should be vacuum lines to the brake booster & to the vacuum canister. It's either a ball sort of thing under the hood or in the DS fenderwell.

 

Correct. The order I would do things is 1) confirm that you have vacuum to the actuator under the battery tray, and that the actuator cable is doing what it's supposed to; and 2) Do the TCCM diagnostic that is explained in the "4x4 no worky" thread in the DIY section.

There is also the sensor on the front diff. that tells the TCCM whether or not the front hubs are locked. If that's bad, and the TCCM things the hubs aren't locked, then the TCCM may not let the encoder motor shift the t-case (I say may because I had a vacuum leak once, and the 4x4 actuator wouldn't work, but the dash lights still indicated that I was in 4x4. Who knows, maybe I had a bad diff. sensor and it fooled the TCCM into thinking the hubs were locked). But based on all that I read on here and other sites, odds are that encoder motor is the likely culprit. The TCCM diagnostic procedure should point you in the right direction, though.

 

Haha...same here. Oops.

 

still no luck. havn't had a chance to check into it at all yet.

however there is a new update. where before if i pressed the button the tccm would at least pop and the lights would come on. Now its not even popping or lighting up. also.. i see people mention a 4x4 light. I did not notice one of those.