How to diagnose horn malfunctions? on 2004 Toyota Sienna

My 2004 Sienna has a dual-tone horn. The high pitch horn has suddenly stopped working; only the low-pitch horn still works. How to diagnose this problem? What must I check? Thank you.

2 answers 1 comment
CK PWR AT THE FAULTY HORN IF YOU HAVE PWR RUN AX. PWR TO HORN AND SEE IF IT WORKS IF NOT REPL HORN
have not checked horn but what is the process to test horn
no horn but fuse and horn relay are good