In the underhood fuse block, locate the FP fuse and relay, check fuse. if both sides have 12v, find relay.. the adjacent one is the horn relay. Make sure they are same relay and swap. Still no FP, then have asst turn key to on and see if FP relay clicks.
If clicks, locate pin 87 socket.. be careful you have to transpose from side to bottom of relay then to relay connector in fuse block. Make sure!!!
Once sure no voltage on that socket, ohm it to frame/chassis/batt grd. Should be less than 10 ohms