It sounds like you have a short in the control module, or a shorted switch. This may not be too hard to trouble shoot yourself, if you purchase a repair manual. They can be bought at most auto parts stores for around $20, and have a full trouble shooting section. You can look this up, and see what it takes to test the control module and associated components.
Other than that, you may need to take it to a reputable transmission shop, preferably one that specializes in 4-wheel drive vehicles.