Horn won't work

Hey all,
my wife has a 2004 Chevy Aveo, actually it's a Daewoo badged to be a Aveo. Problem is the horn quit working. Wondering if you guys had any ideas on which way to go now....

Here's what I've checked thus far:

All fuses check OK, yes all 3 of them.
I pulled the horn relay and it pulls in using a battery charger for power.
I have 12 plus volts at the horn connector and a good ground using a voltmeter to the connector wire and to the negative battery terminal. "0" ohms anyways.
If you press on the steering wheel contacts, you can hear the relay "click".
The horn works OK using wire clips to the battery.

I'm guessing an "open" somewhere, but I'm not really sure where to start. I do not have a wiring schematic, but I am considering picking up an All Data subscription again.

Any ideas from here on?

Thanks

Well I didn't get any replies to this one, I guess no one visits this category or I'm being shunned......LOL

What it was, I found that the ground wire apparently got pinched when my wife had an accident in 2009 and the result was the insulation was cut. After some road salt got in there and enough time elapsed, the wire started corroding, I noticed a bulge about a foot back. I guess there was enough of a connection to show a ground with a meter, but not enough to carry the load of the horn being tooted. I just cut out the bulged up spot and put in a wire splice and siliconed both ends. Hopefully this will hold up for a while.

Toni