What does the wrench light mean on a 2007 Ford Expedition?

The wrench light illuminating in a 2007 Ford Expedition indicates a powertrain malfunction - quite possibly to do with Your 4WD system. You will need to have a diagnostic test performed, as the wrench indicates that some sort of failure code is being logged that will aid in a proper diagnosis. To get a proper diagnosis You can use an OBD diagnostic tool to get the proper error codes that will give You information on what needs to be repaired. Some of the causes for the light to illuminate are faulty or d***y throttle body or transmission issues such as d***y transmission fluid or filter. You can take the vehicle to the dealership and they can perform tests to pinpoint the issue but it will cost about $150 - $200 depending on the amount of labor required.