2000 Jimmy 4wd won't engage

I have a 2000 Jimmy with 69K and no 4wd. It has the n236 transmission. I disconnected the negative battery terminal but this made no difference. I pulled of the passenger side kick panel and can hear the control module click when I hit the Auto 4wd or 4 hi switch. The light blinks yellow like normal but never turns green. It just goes back to 2 hi after about 30 seconds. When it was working properly, the light turns green after about 5 seconds when the 4wd engages. Any I dea what to try next? Is the 2000 with Auto 4wd operated by vacuum?

I had the same symptoms and problem and had to have the transmission control module replaced...about $900.

Check the dates before posting, this thread is a year old.