Per the NV236 Wiring Information thread found in the Tech Article (DIY) section, check the ATC & CRANK fuses in addition to the 4WD fuse.

tntfaguy, If the service 4wd light is on, your TCCM is trying to tell you what's wrong. Rather than throwing parts at it, get the codes read and diagnose the problem from there. It will require a full feature scan tool, but it's better than potentially wasting time and money IMO.

 

ahhhhh, it was the ATC fuse. replaced the fuse and everything seems to work properly now. not sure what exactly the problem was since i have replaced both, the dash switch and the TCCM at the same time. For $60 total in parts I can't complain.

thank you very much startlkk

 

Thanks swart, I had it read at the dealer and they're the ones that said the TCCM was shot and they could not clear it or reprogram it. I'll put the "new" one it in and have it re-read and see if it gets a code. I will also check those fuses.

 

went to do a few donuts in the snow last nite, everything seems to be functioning properly.

thanks again for your help.

 

Swart, if I put in the TCCM from the JY and the service 4wd light is on, could that be stored code from the previous truck or would it be current for my sisters truck? I'm going to be diagnosing Saturday when she brings the truck to me. I guess first thing I'll do is take it down to the dealer or parts store and have them read the code. Thanks-Jason

 

Should be current. The memory would be reset when power was lost.

 

Thanks. Just trying to do some research ahead of time. I read a good thread between you and doodad on this issue....
https://blazerforum.com/forum/showth...&highlight=236

I will check all fuses when I get the truck and all connections. I will install the JY TCCM since I was told the other one was bad. If I get a code, I will have that read and research here. I really only have 1 day to work on this as my sister lives far away so my Dad popped for new parts, dash switch and TCEM, that I got good deals on. If we don't need them, I'll resell on ebay or return if I can. Just want to do my best to get it fixed for her before this storm we get Sunday. Appreciate the help.

 

Actually, looking back over that thread I now know some of my statements are incorrect. As in... The front axle is actually engaged in all 4wd modes. The difference between 4HI and Auto4wd is that the encoder motor will be unlocked and will transition between the 2HI and 4HI positions to vary the pressure on the clutch pack which will vary the amount of power transferred to the front axle. But the rest is good.

 

Understood on the front axle. I actually compared it to my wife's truck when I had it over to the house last time since her system works fine.

Another question, I have read while searching about having trouble getting the new TCEM lined up when installing, some guys mention having the shaft 'pop' into another position when removing the old TCEM, is there anything I can do to prevent that or assist myself IF I do have to pull the old one?

 

Not really. It shouldn't move much and if it does, just put a wrench on the sector shaft and move it back to the position where the encoder motor is able to be installed.