Update: after spending $57, my 4x4 is now a 4x4 again. I bought a new Front Axle Actuator Valve, installed it, and voila. It works great. No more blinking lights; the front end engages just like it is supposed to. GM Part Number for those looking is 15165891. So glad it was something simple. We be a happy camper now. Bring on the SNOW!!!!!