Silverado 1500 7 pin trailer light problem

My 2003 Siverado 1500 7 pin trailer light connector gives me output only for brake lights and hazard warning lights. There is no output for running lights or turn signals. My owners manual shows the "Trailer 6-way" on the "Center Instrument Panel Fuse Block" but I can't figure out how to access it. Could this be the problem?

Look under the dash, just left of the steering column, should be a black plastic cover with a hand twistable nut in it. Might also check under the rear of the vehicle and make sure the wiring harness is tight and not corroded.