I bought my 2002 LS430 last June, one of my todo's was to fix the horn. Nothing happened when I pressed the horn pad.

I downloaded the information from TIS and studied it. After testing the horns individually and then using the alarm I could tell that the horns electronics were good but nothing from the horn, even Techstream didn't show the horn pad being pressed, so I knew it was in the steering column.

So today I finally got time to figure out if it was the Wiring, Clock Sprint, or the Horn Pad Switch. So with the instructions from TIS in hand, I started to work on the car, unplug the battery and then disassembled the Air Bag, tested the horn pads, it has 4 switches connecting to grounds, both worked, I then disassembled the left switch assembly for the radio controls. The horn's grounding circuit goes into it, then it goes up the clock spring connector. According to Toyota you then test the ground on pin number 6. Mine does not have a wire connected to pin 6 on either end of the clock spring. Testing, I can't find a ground to the body anywhere on the steering wheel, I can however find a continuity from the steering wheel to the the top part of the steering column. However the none of the top portion of the steering column is connected to the body ground at all. I found no wiring missing or damaged parts or anything. Just absolutely no ground at all. Oddly all the buttons and controls worked and the tilt worked.

So for a test I grabbed some speaker wire, and shorted out the steering column to the body frame inside the dash, connected my battery (after reassembling the air bag) and then tested my horn, it worked. I then made a new ground wire about 18-22 inches long with eye's on it and connected the upper and lower steering column. I have a good ground now, and now I can use my my horn.

I had googled this and never found a solution, so I'm posting this here in the hopes I can help someone else. Should have took pictures...

Hope this is clear enough, I'm pretty tired.

 

Is this a common issue on the LS ?

 

I don't know, It could be unique to mine. It' also possible something is missing from a previous owner working on it. My telescoping also didn't work when I got it.

 

I think it might be. I bought mine last spring with 218k miles, and now at 235k miles the horn is working off-and-on intermittently/randomly. One instance it would work, another instance it won't.

 

So I attached the ground wire on the upper column (red arrow pointing to screw), run the wire down and across to the right side and tied it to the main wire harness, and down through the white shroud covering the excess wire from the wire harness, came down the back of that and connected it to the brake pedal return spring mount at the lower side of the steering column.

 

"So with the instructions from TIS in hand, I started to work on the car, unplug the battery and then disassembled the Air Bag, tested the horn pads, it has 4 switches connecting to grounds, both worked, I then disassembled the left switch assembly for the radio controls. The horn's grounding circuit goes into it, then it goes up the clock spring connector. According to Toyota you then test the ground on pin number 6. Mine does not have a wire connected to pin 6 on either end of the clock spring."

Thanks for your help.
What connector are you referring to testing "Pin 6" on?

 

​​​​​​That was 4.5-5 years ago. If I remember right this is the connection going into the clock spring assy under the airbag, it connects to vehicle harness under the steering column.

If you have access to a computer with the Toyota Diagnostic software, it has a horn test in it, this won't test the connection to the horn pad though, just the horn circuit.
I think the ground is lost and never properly restored if the telescoping is extended to far, it seems you can get it to extend farther than intended if you keep pushing the button. Horn has never given me trouble since installing that ground wire.

 

I took it apart and put it back together now it works...

HUH!!

Thanks for your reply...

 

I spent hours on this and haven’t found the cause. I experienced this problem while changing the telescoping motor. I was originally confident that the ground connection happens through the telescoping bolt. The rubber

bushing that attaches the bolt to the upper steering column has a metal clip on it and I can’t see any reason for that other than to ground the steering column to the stationary metal nut which the telescoping screw goes through. that rubber bushing gets worn out and it’s possible the contact gets lost.

when I took the mechanism apart one of the things I did is pull the wheel all the way out.

when I reassembled everything the horn was back.

however then determined to figure out the cause for initially losing the connection I took apart the mechanism piece by piece and tested - and even with the busing and motor removed and disconnected I couldn’t reproduce the problem. it seems that it’s the telescoping motor and the bolt. It looks like there are gremlins somewhere in there and I give up.

while the motor was disconnected the screw was loose and the horn didn’t work - I used the wire bypass method mentioned in this thread to make the horn work during that time.