2009 H3 145k miles. No codes. Newer battery.
Battery tests as ok at O'reilly.

Has anyone experienced this?

Three fast horn honks happen as I begin to turn the key to start. Google search indicates voltage, oil pressure or crank sensor, but if I removed the battery and charged it then replaced, the codes should be cleared. There are zero codes stored or showing on the dash.

Thanks!
Gabe

 

Hummer H3's horn honking when the ignition is turned on indicates a faulty or stuck horn relay, a short in the steering column wiring, or a damaged horn switch. To troubleshoot, you should first test the horn relay and inspect the wiring for shorts or damage. If those are fine, the issue could be a stuck horn switch within the steering wheel itself, which can be caused by debris or a broken spring.

Troubleshooting steps:

1. 1. Locate the Horn Relay:
   Find the horn relay in the vehicle's fuse box and test its functionality.

• 2. Inspect Wiring:
  Examine the wiring harnesses connected to the horn and steering column for any damaged insulation or exposed wires.
• 3. Test the Horn Switch:
  Gently tap the horn button to see if it's stuck, or remove the airbag to inspect the contacts for debris or wear.
• 4. Check for Shorts:
  A short in the electrical system, particularly around the steering column, can cause the horn to activate.

Potential Causes:

• Faulty Horn Relay: A stuck relay is the most common cause of a spontaneously activating horn.

• Wiring Issue: A short in the wiring, especially near the steering column, can create a faulty circuit.
• Stuck Horn Switch: The physical switch in the steering wheel can become stuck due to debris or a broken spring, leading to a constant signal.

What to do:

• Swap Relays:
  Test the horn relay by swapping it with an identical relay from another non-essential system (like the rear defrost) to see if the horn functions normally.
• Disengage the Horn Button:
  With the battery disconnected, the airbag and horn switch can be safely disconnected to test if the horn stops.
• Professional Assistance:
  If you're not comfortable working with the electrical system or airbag, it's best to have a qualified mechanic diagnose and repair the issue.

 

I appreciate the thorough response.. here are a few more specifics.

• The actual horn functions properly.
• The horn seemingly beeps properly with alarm activation and deactivation.
• The horn only beeps 3 times ONCE if you take the key out then turn key. The car doesn't have to start.
• No offroading, water intrusion or impacts have happened.
• Only electrical difference was I had a FM bluetooth receiver in the cigarette socket overnight this week.

I'll test some continuity on the horn tomorrow. Maybe jiggle or remove the relays.

 

Are you still trying to use the crappy azzed OEM Battery Terminal connectors. If so, big mistake. Remove and replace with a quality aftermarket set like Stingers or your favorite brand. First mod to be done to every H3/H3T.

 

The battery connections have been replaced but they seem to be cheapish quality. I think they are aluminum and the negative terminal requires 2 copper post shims to make the connection secure as that post is smaller. They are firm connections with zero corrosion, though.
I swapped the horn relay with the fog relay, no change.
I unplugged and jiggled the wiring connector under the steering wheel.

 

Do you have an aftermarket alarm or remote start system installed?

 

I haven't installed anything but noticed some wires lead to a small controller under the dash.. i'll post a photo next time i go out

 

Is that an aftermarket unit?

 

Yup, at least my 09 doesn’t have that. If its part of an aftermarket alarm system then that’s probably the source of your horn chirps.

is your keyless entry remote the standard H3 design?

 

Sorta standard, but with a trunk button. I tried a new battery in the remote today, too. I'll wiggle under and see where that little box connects and see if that resolves the issue. I have had the H3 for 4 months and this just started a few days ago.