Hey guys I'm a newbie with this electronic 4wd systems. Recently I had a 2000 Blazer given to me, really good shape, little to no rust, clean and only 125k. Currently the 4wd selector switch has no power, it doesn't light up and the buttons do nothing when pressed. It has a 3 button switch. The #15 fuse is good and doesn't appear to be burned or damaged. I'm gonna have a look tomorrow at the connector on the TCCM and see what it looks like. I know this switch get's power from the TCCM, so my question is, that if the TCCM has no power, what do I do from there ?? TCCM is brand new from AUTOZONE but was installed by the previous owner. Thanks guys, PB

 

I just went through this with a 1999 Blazer I bought cheap but the 4wd didn't work. I found some info on this site. I also have a working 1998 and swapped out the 4wd selector from it and it was black in the 1999. I went to the TCCM behind the passenger kick panel, and I found voltage going in on pins C4 and C5 when I pressed the 4wd selector. I also checked that C10, D10, D12 and D13 were continuous to ground. So the TCCM should have been working. I found a used one cheap on ebay, it arrived last week and now the 4wd works!

If your TCCM does not have power, and the fuses are good you may be looking at a wiring issue.

 

ok here goes. I have a 2000 blazer. I had the same issue. Two weeks ago I had to spend about 200 at the parts store. One of my goals was to get the 4x working. Turns out I had two issues. A vacuum leak was the first most obvious issue. My vacuum line for the 4x actuator had completely broken above the engine and I had no idea. Second the actuator was completely destroyed. What did they expect by putting a rubber diaphragm in the engine bay? Your engine bay is likely the same as mine, I don't know what version you have if it even matters. Check under the battery plate, you'll need a 13mm,7,8 or likely a 1/4". The bracket for the actuator is held on by two or 3 bolts in the passenger side wheel well. The diaphragm is likely ripped. New 4x actuator was 50$ at autozone. I hope this helps.

 

Would a vacuum leakcause the indicator light's not the switch to not work though ? That wouldn't make sense though....seems like the electronic part would have to occur first ???

 

im pretty sure I replied to the wrong post...it was very late. Check number 15 fuse I think driver side. It's a ten amp. After that pop the switch out and follow the wiring. The vacuum issue wouldn't cause the electronic issue but always good to check.

 

Check ATC fuse in underhood relay center.

Here's additional info on 3-button 4WD.

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

 

Hey LES thank you very much for the info and schematic on this thing, however I was incorrect in my OP. This blazer has a 4 button switch, not a 3 button. How do I find out if this switch is the correct one for my truck? It appears to be a brand new switch also but was installed by previous owner. Thanks.

 

https://blazerforum.com/forum/2nd-ge...-blazer-89044/

 

Easiest way is to check the RPO label in the glove box.
If you have NP8 listed it's a 4-button system with Auto 4WD
If you have NP1 listed it's a 3-button system