aloha..
we just bought a 96 blazer that the owner told me wouldn't go in 4hi.
I found this tip online.
http://www.alldata.com/techtips/2002/20021230b.html Jim Grant's Tech Tips
'96 GMC Jimmy, 4WD Won't Engage
Q: I've got a '96 GMC Jimmy, I didn't use the 4WD much over the last year and when I tried to engage the 4WD, the HI light first flashed then did nothing so I tried the LOW and it did the same. It is now showing no response at all when pushing on either button and does not engage in 4WD. Any ideas on what I should have a mechanic look for to fix?
A: The most common problem we see with these systems is an encoder failure. This means the computer module that controls and monitors the 4WD shifting motor doesn't know where it is. The computer needs to know the location of the shifting motor to perform correctly. If the computer loses location information it stops responding. Diagnostic codes can be extracted but, because you have not used your 4WD much it may be all that you have to do is to clear the computer so it can start over. Turn the ignition switch off and remove the fuse marked T-case (it should be a 20 amp fuse). Wait a minimum of 3 minutes then replace the fuse. Once the fuse is replaced turn the ignition switch on & off 5 times. Then start the engine and push the 4 Wheel HI button. If the system starts working, great. Be sure to exercise the 4WD system regularly to prevent a reoccurrence. If the problem returns then you need a technician familiar with your 4WD system to get into some diagnosis.
The fuse box is on the left side of the dash right inside the driver's side door. In my case it was a 10 amp fuse marked transmission on the legend inside the cover. I pulled the fuse out, left it out for about 5 minutes, reinserted it, turned the switch on and off 5 times, started the truck in park and pressed the 4hi button. The light lit, put it in d and it worked.
Stopped, put in in park, pressed 4lo and it worked.
Told the guy we'd buy his truck.
When we called the guy to pick up the truck, he told me it was stuck in 4hi and he couldn't get it back in 2wd but I figured It would need exercise... like Jim said.
We stopped to eat on the way home and repeated the fuse trick.
It was still in 4hi, the lamp was lit. I just kept pushing the 2wd button on the way...I could hear clicking noises.. and finally it just shifted to 2wd.
Will exercize and check vacuum lines like tips on this forum suggest.
good luck braddah
Great stuff... thanks everyone.
