Sorry to bother y'all for such a silly question, but under which front fender does the horn live?
I noticed yesterday that the horn wasn't chirping when I locked my car ('07 2400 LT) and then discovered it wasn't working at all.
I don't know whether it's a loose wire or if the horn's crapped out, but I need to find it first.
My Haynes manual says to "Remove inner fender liner," but neglects to point out driver's side or passenger's side.
Much obliged.

 

Have you done the obvious parts first? Fuse, relay etc.

Passenger side

 

I don’t like to contradict you Donbrew, but the horn is on the driver’s side under the headlight area

 

donbrew: In short, No, I haven't looked at anything yet other than the shop manual.
Is the relay in the fuse block?

 

In the under hood fuse box, the horn fuse is #60

 

Thanks for the diagram.
As you were responding to this, I was under the bonnet. Fuse #60 is intact, and I swapped Relay #55 with another, but the horn remains quiet.
Next step is the horn itself I guess.

 

Yes, I replaced mine with a two tone set from a 2012 Camaro SS, plug and play harness

 

No. The next step would be to check the wiring at the horn. Get to the horn and check that it's getting current when the horn button is pushed.
Got current, the horn is either bad or not grounded.
No current. Somewhere between the horn itself and the steering wheel.(steering wheel button, clock spring or wiring)

 

Those wire frame pictures got me again!

Here is the schematic:

 

Just to follow up on the horn issue I raised a few weeks ago.
(Thanks Oldblue, the horn is on the driver's side.)
After getting things apart, I discovered a terrible splice-job on the horn's wires. I have no idea what would have cut the wires requiring the splicing in the first place, but it was a crappy job and as soon as I started jiggling the connections, the horn beeped its approval. A couple of Sta-Con splices and a few zip ties later, no more horn problems.
Thanks for everyone chiming in.