2000 Chevy Impala horn stays on

Welcome to the forum. With horn relay removed, check terminal E6 for ground, use led testlite connected to battery voltage, touch terminal, if lite comes on, the circuit is grounded. It shouldn't ground unless you honk the horn. Possibilities, the wiring circuit in the steering column/ horn button is shorted to ground. There is another possibility, if you have an entry type theft system, the bcm can ground that circuit.