2000 Ford Ranger loading up PO176

P0176 fuel flex fuel composition sensor circuit malfunction.

I would try cheap and easy first. Look under the truck near the transfer case directly below the driver seat and you will find a 40-pin connector. It doesn't like water and has a habit of shorting all sorts of things together that relate to the rear half of the truck. Use a 10mm socket or wrench to open up the connector and you may find water/dirt/corrosion inside. Clean and dry with electrical contact cleaner and reassemble. If you can find dielectric grease (about $7/tube at auto parts, electrical supply house or Ford dealer), pack the pin area full of it before reassembly - it helps keep the water out.