Horn not working in Hyundai Trajet

check list --start with power and connections then switches wiring and components

There are several. Plus the module itself. Check the fuses first, Then it is best to have the codes read to find the problem. Messing with airbags can be hazardous.

First thing first, use IBD II device to find out the check engine code, and you start troubleshooting from there.

on the gearbox will have a connector with 2 wire coming from it and the end of switch will have a nut shape so can be undone

check masterswitch at driversdoor to see if switch has power or faulty relay.

i believe there aare 2 fuse boxes in the tiburon one under the hood and one under dash

Is under crankshaft pulley.

simple circuit, but can be hard if problem is switch in steering wheel. First check fuse and relay at fuse box. relay should click when horn button on wheel is pushed. If relay doesn't click, either button or relay is bad. If relay clicks, test for voltage at horn. You can use a simple test light available at the auto parts store if you don't have a voltmeter. If there is voltage at the horn, replace horn.
If relay does not click, replace relay to see if that fixes your problem. If new relay doesn't fix, you have a bad switch in the steering wheel or possibly bad wiring. cannot help you with switch as it's different on every car. any questions--let me know.

does the relay energize when you push the horn button or ring
take the horn out and test it to the battery using a couple of test leads/alligator clips
you have a bad horn, or a bad switch, or a bad connection

if i'm looking at the right diagram, the horn-a/c fuse & horn relay is in the underhood fusebox. if your
a/c clutch is working then you have power there. short of diving in with a multimeter or computer-safe testlight,
i would listen for the horn relay to click when the horn button is pressed. that circuit is hot all the time and the horn switch
grounds the horn relay. if you hear a click then most likely you have a bad horn/s. if you don't hear a click then you have a
bad horn switch or bad clockspring in the steering column. and .... there's always the possibility of just having a bad
connection somewhere in that circuit. if you see another relay with the same part number as the horn relay,
try swapping relays. good luck ........