2009 Hyundai Accent cruise control install

I just installed a 250-1799 cruise control unit with clutch switch into my car. This was an easy install with only a couple of electrical splices.1) power from new harness to power line in fuse box 2) power from on side of brake swich to new harnes 3) other side of brake switch through cluch switch to new harnes 4) Harness to VSS signal in diagnostic plug. Unit works great BUT! If you hit the horn it doesn't blow but the CHECK FUEL CAP alarm lights up on the dash.
I've gone over all of my connections and don't see any exposed conductors thar could be shorting out. The only thing I can't get a good look at is were all the wires feed through the bulk head by the drivers feet.