Unusually 4wd behavior in 1999 GMC Jimmy
4-button switch seemed to work fine at first but after getting stuck noticed the front wheels would only lock in when switched to “Auto 4wd.” Transfer case would shift to low range and back out, it would go into “neutral.” All of the lights were working but maybe the TCCM was not locking the front wheels in “4hi” and/ or “4low.” I think the actuator under the battery is working because the “4wd Auto” would lock the front wheels.
Now, at start up the truck mysteriously selects “4wd Auto” or “2hi” and pushing the other buttons has no affect on it. Those two work properly with respect to 2wd or 4wd but I cannot switch it. I had the GM dealer in town run their scanner on the Jimmy and they concluded a bad switch in the dash. I ordered the switch from AMAutopart, on eBay, but it did not solve the issue, I even tried another switch but still nothing. I have unplugged the TCCM while the motor is running and I hear clicks from the TCCM.