Q: What could be the likely problem of an "check advtrac" light staying on in my 05 Ford explorer ( 4wd )

Advancetrac is your vehicle’s traction control system. Your vehicle is equipped with wheel speed sensors at each of the four wheels which monitor wheel speed while relaying this information simultaneously to the ABS and traction control system which are controlled by the car’s ECU. When the ECU senses an abnormal speed given specific conditions, it engages the ABS or traction control as needed to control the vehicle properly and safely. Occasionally, these sensors can fail or become faulty working intermittently sending inaccurate signals to the ECU. When this happens, you may experience the symptoms you have described. The ABS or traction control system may be inadvertently activated by these false or inaccurate signals. I would suggest having a professional from Your Mechanic come to your location to diagnose and inspect your vehicle.