A code P0176 can indicate a number of problems with a Ford Ranger, but it most commonly refers to a malfunction with the fuel composition, or flex fuel sensor. It is likely that you will have to replace the flex-fuel sensor, which is sadly a rather pricey repair that will cost between $300 to $400. Before actually taking the vehicle to a garage, however, check out the entries on this forum, which all relate to the problem that you are experiencing.