Could be a couple of things, but I had the same problem with the blinking. I've found the rubber line feeding air pressure to the diff was leaking and the air pump would run on and on, then break off. Once computer determined it's necessary again, the pump would run again. I just replaced the rubber line with a fuel rubber line. Fuel line is better rubber, much thicker, and is reinforced.
Check the small rubber line feeding from the frame to under the front diff. Take some soapy water and apply it to the rubber line to locate the air leak.
Place the vehicle in park, key in run position, motor off. Pull the rubber line off the steel line on the frame and plug that with your finger. You should feel the air pressure from the pump. You should also here the pump running. Someone else will let you know if the blinker stopped. If it did, this is a strong indicator that is the problem. If not, check the other rubber lines to the pump. The funny thing is the pump is located above the bumper, behind the grille. The line is rubber, then steel, rubber insulated. It runs out to top of radiator, along the inner wheelwell, then back down to the frame crossmember, to the diff. A way long way to get to the diff.
I think I have a few pics in the webshots. Not much of a picture, but
http://community.webshots.com/photo/107940331/107941409HmLYNt