I own a 2001 Dodge Durango it has 115,000 miles on it im not really sure what size engine it is at the moment..... anyway the service 4wheel drive light is on and since that light has come on the radio buttons on the back of the steering wheel wont work the back windshield wiper wont work. the water will still squirt on the back window but the wiper wont work. how do you serive 4wheel drive? and is there anything other than the 4wheel drive not working that would make all that not work? please help me.........

thank you