I have a 2001 2 door Blazer ZR-2 and it has developed a 4WD issue. I can engage 4LO without a problem, but when I select 4HI or Auto the lights just blink for a while then switch back to 2HI.

I'm guessing it's some kind of module but I'm not sure where to look. Any ideas would be appreciated.

Thanks,

Dave

 

Welcome to the site.

I have not had to fix a broken modual yet. However it should be located in the t-case. Someone else should be able to provide more info on it.

 

try disconnecting your battery and resetting the computer. see if it works then...if it dows its probably the shift motor control module...thats what it was in my truck

 

Thanks for the replies and the welcome. (been out so sorry for my slow reply)

I disconnected the battery, no difference. I found the TCCM and unhooked and checked the connections on it and see no difference. I do hear it "click" when I change from 2HI to 4HI but it doesn't seem to do anything and the 4HI light flashes for a while before returning to 2HI. It works the same on Auto 4WD

When going to 4LO the transfer case changes to LO, but I'm not sure the front engages, it seems that it's really in 2LO.

I'm still in debug mode, any help is apprecaited.

 

I had the same problem. When the "service 4wd" lamp came on I was on dry pavement in 2hi. I took out the tccm and found that one of the chips on the board looked burnt out. A friend who works at a dealer, says they can "go" sometimes. He says he use to replace the shift motor only to find out it was fine and then replace the tccm. So I ordered one from Autozone ($339.00?) and it was from a salvaged vehicle. A new tccm from the dealer was about 60.00 more. It immediately worked.

My tires were quite worn and replaced them with a taller set. About 2 days later It wouldn't engage into 4auto. (it's winter here.) I took it out back in 4hi and spun the wheels in the muck. Now its fine.

Anywho, take it somewheres where you can see front wheel slippage. Even in some wet grass, i.e. your neighbors. There you'll see if the front is engaging. Take the cover off the tccm and look closely at the cicuits. Any sign of discoplored chips may indicate it's shot.

You can drive w/ it disconnected, but only in default, 2 hi. Good luck, happy four wheelin'!!!

 

I think this one is heading to the dealer.

I did the disconnect tricks, checked connections, etc. and still no 4WD. I can get what looks like 4LO from looking at the lights, but it's really 2LO because the front never engages.

Also sometime during this diagnosis the A/C has stopped working. I have fans, but the compressor never comes on. I know it's winter, but I live in Florida.

 

That sucks man. Hope they don't take you for a ride! Good luck.

 

I was told $50 for diagnostics and they would apply it to the repair if they did it.

I'm thinking if they tell me what's wrong I'll do it. I've got way over $50 of my time and frustration in this already so it seems like a bargain.