If your Lincoln Aviator's cruise control is not functioning properly, start by checking the cruise control fuse in the fuse box and replace it if necessary. Next, inspect the cruise control switch on the steering wheel for any visible damage or signs of wear. If all appears to be in order, it is recommended to consult the Lincoln Aviator automotive repair manual for detailed diagnostic procedures and potential causes specific to the cruise control system. The manual will provide step-by-step instructions on how to test components and repair any identified issues.