Hi all, I thought I would share some sleuthing I've been doing to fix my horn on my 2015 5th Gen 4Runner in the hope that it will help someone else down the line.

The main symptom is that pressing the horn on the steering wheel doesn’t sound the horn and I can hear no other noises like relays opening/closing. There are a few different threads on this across multiple forums with varying potential causes. Some of the main ones I’ve come across are:

• A bad horn ground
  - The 2 main horns that sound when you press your horn are grounded through their mounting bolts to the chassis. If this connection is bad, they won’t ground properly.
  - You can test this ground point by using a continuity tester or a multimeter.
  - The horns are located just in front of your radiator on the drivers side. You may need to remove the plastic cover to see them.

• Damaged spiral cable/clock spring
  - Results in a poor ground connection to trigger the horns.
  - Usually (but not always) accompanied by other buttons not working on the steering wheel.
  - Sometimes the horn may work while you turn the steering wheel or at different steering positions.

• Failed horn
  - The horns themselves can fail, but can be tested easily.
  - You can test them by grounding the horn through the mounting bolt, disconnecting the plug that leads into them and connecting a separate wire from your battery +ve directly to the horn connector. You should hear the horn sound. If it doesn’t, you need a new horn.

• Faulty Integration Relay
  - Also known as the “K-Unit Relay” or No. 1 Integration Relay
  - Doesn’t look like a typical relay. Is located in the fuse box on the drivers side of the engine bay and houses 4 fuses.
  - There is information in the Toyota Repair Manual for the 4Runner on how to test whether the integration relay is faulty. You can pull it out with the wires still attached. I found I could get it out just enough to be able to probe the wires/pins.

Other info to note:

• The “Security Horn” is separate to your driving horns and may still work when pressing the panic button on your key fob. Mine worked while my driving horns did not.

In my case I found the following:

• Horn fuse tested OK.
• Horn grounds tested OK.
• Horn wasn’t working at any steering wheel angle, all other buttons were OK.
• No +12V at horn +ve connector when the horn is pressed.
• Connecting between battery +ve to the horn ground wire on the inside of the steering wheel gives 12V when the horn is pressed.
• Connecting 1C Pin 7 of the integration relay to the horn ground wire on the inside of the steering wheel gives 12V when the horn is pressed.
• Connecting 1C Pin 8 (Grn/Red) of the integration relay directly to battery +ve makes the horn sound.
• Testing between 1E Pin 1 and 1C Pin 8 when there is no voltage applied to 1C-6 and 1C-7 gave 0 Ohms. This should normally read 10kOhms or higher and the repair manual states to replace the integration relay if this is not the case.

With all this considered, I have decided to order the Integration Relay part number 8264160080 and replace it. I will report back here with any updates but for now I hope this helps someone who was in a similar boat to me and was scratching their head! I will try to include some photos below.

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Look at the pin where the wires lead and make sure the is no black scoring going on, and the pins of the old relay. Small wire brush works best to scruff them up.

Different vehicle but something else to consider.

I have a 99 Sienna and the horn quit working. I found a lot of threads about the clock spring being bad, but everything else work; cruise control, radio, etc. I happened across a thread where the person said that there is a bearing in the steering column that can rust and prevent a good ground. I took off the steering wheel and clock spring, put shop towels down on the floor mat and shot WD-40 into the column. Out of the bottom, in front of the brake pedal, poured out rusty WD-40. I got that all cleaned up and put it back together. We haven't had a problem for several years now. Make sure you use some blue masking tape to mark the location of the steering wheel and clock spring before you take them off.

Good tip. If replacing the relay doesn't solve the problem I'll have a closer look at the plugs/pins.

Funny you mention this - I had initially started writing a section about this potential cause as well but hadn't seen much about it happening on a 4Runner. Definitely something worth investigating if the other fixes don't work! Thanks for your input.

Well, update.. it wasn't the integration relay. Part arrived and I installed it with no change. Horn still doesn't work.

I'm going to have a look around the clock spring and associated wiring to see if anything is loose/damaged. If anyone has any other thoughts let me know!

If you have a good ground on the steering wheel like you mentioned then the rusty bearings are not your problem. I don't think this is common issue on 4Runners either.

When my clock spring went bad it had a bad ground on the steering wheel. IE continuity test with multimeter. When the steering wheel was rotated a few degrees in each direction the horn would work, the continuity would register and beep since the circuit was restored. The leads me to believe the clock springs ground the steering wheel in the 5th Gens. The clock spring could probably fail in more than one way and yield the results you are getting also.

If you want to test my old clock spring assembly let me know. I can ship it at your expense.

Edit: Just realized you are in Canada so probably not worth the shipping expense. You can find the assemblies on amazon if you want to go that route. OEM is expensive but the airbag is pretty critical so thats the route I went.

Appreciate your feedback and the offer! I'll see how I go with a bit more investigation at the clock spring. I was registering 12V between the horn ground wire and battery +ve but no beep from the multimeter so maybe it is a ground issue. For the continuity test, would I test between battery -ve and the horn ground?

With multimeter in Resistance mode (ohms, Ω) test from some bare metal on the steering wheel to bare metal on your frame (you can use the nearby door bolts or latch that are not painted). If you have a bad ground you will not hear the beep or register any resistance, this was my results and a new clock spring fixed the issue. A good ground is required on the steering wheel to complete the circuit when the horn is pressed.

If you fail the above test you could try running a temporary ground (with jumper cables) between the points tested above. With this new ground setup does the horn work? Disconnect the battery and air bag while working and only reconnect the battery when performing tests.

Getting 12v between the battery and wheel is a good sign but doesn't tell the whole story until continuity is checked.

Similar situation with my 2015 SR5. Was getting all good readings and indications with the steering wheel turned left and right, yet nothing when centered. No other issues with any buttons or operability. Tested the clock spring pin connections to ground and found the ground pin, had an open when it should be ~ .1ohms. Ended up ordering an after market clock spring, and after replacing haven’t had any issues. Did this January of this year.

Can you hold the panic button down on the remote and get the horn to go off?

Thanks for these tips! I checked again last night and I think it is indeed the clock spring. Tested continuity through the clock spring pins and the horn ground didn't seem to be working while the other pins tested OK. I have ordered an aftermarket replacement and will see how that goes. Opted for just the clock spring itself so will swap over the steering angle sensor.

Yes - but the security horns are separate to your driving horns. I mentioned this in my first post.

So there's no problem with the other controls on the steering wheel? Radio, turn signals, cruise?

Before you remove the air bag be sure to disconnect the battery. There is also a breaker/fuse for the air bag but I don't know which one it is on the T4R.

Before removing the steering wheel, use some tape (I used the blue 3M masking tape) showing the current position so you can put it back in the same place.

Good luck, I hope it fixes the problem

Same here and I also went with an aftermarket clock spring ($19 - eBay), did this about couple of month ago.

The arm/Disarm beeps are a separate siren, when the alarm goes off or you set off panic that is the horn honking.

Interesting, I'll have to try this.

To update everyone on the progress: it ended up being the clock spring. I was surprised that everything else on the steering wheel was working apart from the horn but there you go! I bought just the clock spring itself from Ebay and switched over the steering angle sensor which is very easy with a few plastic clips.

Thanks to everyone on this thread for the info and tips. This forum is a great resource and I hope this thread serves as a good addition to the knowledge bank if anyone else runs into the same problem.