Steve Ross

Does anyone know why the built in trailer wiring harness on a 2001 RX300 would have no power to it after the 'towing' fuse [20A] is inserted? The fuse is good and there is power to one side in the fuse box. The trailer harness is located up under the tank and has 4 prongs as expected. The ground wire is ok, but no power to the other terminals. Any ideas [or a wiring diagram] would be appreciated. Thanks, Steve