Have a 99 Blazer LT 4WD with the POS 4 buttons.

Been trying to fix the 4WD since summer, replaced the TCCM, transfer case motor, and the switch already. Whenever the vehicle is turned on the lights on the switch blink as they are supposed to then the switch goes blank, no lights at all. The relays in the TCCM go click click then the POS (piece of ****) S4WD light goes on. Already brought it to the dealer which prompted me to replace the tcase motor. Already checked the fuses, replaced some wiring, and no corrision, I basically know the system almost inside and out now unfortunately.

In another issue my ABS was acting up in the summer and I found the cable was severed on one hub, replaced it and it still skipped forward 10 feet or so when normally it would stop. So the other ABS sensor must be bad I'm figuring and at that point I said screw it and took out the ABS fuse not wanted to dish out another 100.00.

So my questions..
- Could the ABS be causing the 4WD issue? Maybe the TCCM relies on the ABS to work or a speed sensor in the hub?
- Could low front differential fluid cause the problem? It leaked, replace the seal and it still leaks...
- When I put the new tcase motor on the tcase only seemed to have 2 detents. Not exactly sure on this. Could the tcase be broken and causing the S4WD issue?
- Could not having the front drive shaft on cause this? I didn't put it back on since I put the tcase motor on as I thought I'd have to screw around with it more.

Any other ideas as I'm about ready to give up and let the truck be a
2wd truck. That or I'll write a letter to Chevy and ask them to rediagnose it for free as it wasn't the transfer case motor that was causing the issue.

Thanks

 

What were the codes present in the tccm?... The service 4wd light indicates that there are stored codes that may just point you in the right direction. Throwing parts at it is a sure fire was to develops the crappy attitude that you seem to have...

 

The code in the previous replaced TCCM said the resistance was bad at the encoder motor. That problem was corrected by replacing the encoder motor. I replaced the TCCM itself as my soldering skills managed to hose the previous one, long story.

I'm just frustrated that I cannot fix this myself and I'm essentially forced to go to the dealer to get it scanned rather then something like Autozone or similar. It would seem that this would be a lot simplier if this was just a manual system rather then an electronic and unfortunately being a 4-button system I cannot change it to manual without replacing the tcase which I'm considering. Guess my best bet is the dealer as I doubt the ABS issue has anything to do with it.

Thanks for the reply.

 

You're right, ABS system doesn't affect 4WD system. And if you only can move to two detents on the transfer case that'll put the system into a default mode. There should be 4 and if the motor can't cycle the whole range when you turn the key on you'll either get a motor or an encoder error.