Ugh, horn keeps firing, please help (1 Viewer)

[DoctorJay]

I've searched the old threads and come up with a couple of potential problems. Just wondered if a new posting will find more people who have had this problem.

Something's been wrong with the horn since I got all the injectors replaced about a month ago. (My LC problems are decreasing in magnitude, which is good). The horn didn't work when I got it back from the shop. In the box under the hood is a 10A fuse and a relay. The fuse was blown (replaced it) and the relay looked fine. Pressing the horn switch on the wheel gave a click (from the relay) but no horn. I replaced both horns, and it worked fine.

Fast forward 3 wks. About 1:00 this AM, I wake up to a blaring horn. It was mine. Not the alarm, just constant. Hitting lock/unlock/panic didn't help, so I popped the hood and pulled the relay. I tried replacing the relay a couple times before work today, and the horn would start firing again, on its own, after a few seconds.

So AFAICT the problem is a closed circuit somewhere on the upstream side of the relay/fuse. Any common problems that can lead to this? I've read about dirty contacts or chafed wires. The first is a simple fix, the second costs $$$$$$$$ and requires pulling the dashboard.

I'm also thinking that the failure of the OEM horns and fuse probably happened because the truck sat unattended at a shop for a couple weeks with the injector thing, and the horn must have fired off overnight to the point that the horns failed and the fuse blew.

Any wisdom would be hugely appreciated.

 

[100 TD]

I'm also thinking that the failure of the OEM horns and fuse probably happened because the truck sat unattended at a shop for a couple weeks with the injector thing, and the horn must have fired off overnight to the point that the horns failed and the fuse blew.

Any wisdom would be hugely appreciated.

No wisdom but the 2002 circuit shows the relay for the horn is "Ground" switched, so anywhere between the relay and the switch in the wheel can ground out and turn the horn on. Most likely problem is in the wheel itself, pull the wheel and check for worn or loose switch or the connection cable/ribbon from the steering coloumn may be worn through. That to me is the most like place of shorting or failure, you could of course just pull one wire from the connector on the steering column which goes to the relay and see if you get any more problems. If you don't then it is likely in the wheel or ribbon cable. From my diagram the wire is a green with orange stripe, pin number 7 of a 22 pin connector. (This is from a 2002)

 

[DoctorJay]

Thanks, that's a good place to start. I'm pretty nervous about pulling apart the wheel on an airbag-equipped vehicle, though. I know it's not cheap to repack the airbag if I detonate it, plus the cost of a new pair of underwear for me. Have you done this before?

 

[9toys]

i responded to someone's post a week or so ago with a similar problem. My 99's horn was going off on it's own. it turned out to be the P2(I think) relay which is somewhee near the dirver side foot. It was corroded. rather than relplace the relay($2K), the tech coated the relay with waterproof grease after scraping away the corrosion. That's been a couple of years ago now and it's still working fine.

 

[Wellcraft19]

Even on a Toyota, a relay for $2K sounds awfully expensive...

 

[9toys]

i was stunned at the price but i think most of the cost is the labor as they said they had to remove the entire harness, which entails removing the dash. the tech didn't want to do it either because he said i would become a regular with dash rattles and squeaks. He said if the grease wouldn't work, he thought he could re-route it somehow without replacing the relay. so far, we haven't had to do that. I'm keeping my fingers crossed. I'll use a bicycle horn before i pay 2k.

 

[DoctorJay]

i was stunned at the price but i think most of the cost is the labor as they said they had to remove the entire harness, which entails removing the dash. the tech didn't want to do it either because he said i would become a regular with dash rattles and squeaks. He said if the grease wouldn't work, he thought he could re-route it somehow without replacing the relay. so far, we haven't had to do that. I'm keeping my fingers crossed. I'll use a bicycle horn before i pay 2k.

Wow, no kidding? I actually read your post in the other thread about this. I'm kinda surprised that Toyota would put a relay somewhere that the dash has to be pulled to get to it. Relays fail. So the tech was just talking about running a new wire from the steering wheel to the fusebox under the hood, and maybe punching a new hole in the firewall to get it through?

 

[100 TD]

Thanks, that's a good place to start. I'm pretty nervous about pulling apart the wheel on an airbag-equipped vehicle, though. I know it's not cheap to repack the airbag if I detonate it, plus the cost of a new pair of underwear for me. Have you done this before?

I have on my Ford, but not my cruiser, I can't remember if I just pulled the fuse or disconnected the battery. Don't forget the airbag stays charged with power for at least 90 seconds after disconnecting the power.(Could be longer, do a search, I am sure there will be a topic already covered)
As I said if you leave the wheel and just pull the wire you work out if it is in the wheel or not.
I haven't read the other post about corrosion, but if there is moisture or corrosion on the relay or wiring and it tracks to ground the relay will energise and the horn will go off.
The diagram I have shows the relay under the bonnet but the connection from the horn switch appears to go via a connector in the back of the dash and also via the left kick panel.

 

[DoctorJay]

Are there 2 horn relays? I know in my '01 there's one under the hood in the fusebox (I know because it's labeled, and it's in my pocket to keep the horn off). So is there another one under the dash?

 

[100 TD]

Are there 2 horn relays? I know in my '01 there's one under the hood in the fusebox (I know because it's labeled, and it's in my pocket to keep the horn off). So is there another one under the dash?

As said previously, the relay is under the hood, but also said that this is a 2002 diagram, but I doubt a change. All wires run in a harness, and generally more than one harness, and go through different connectors and parts of the car to their final destination, not just directly from point A to point B.

 

[miraloiza]

Check the horn switch on the steering wheel. You might find this is your problem. Pull back on it while the horns are sounding or better still disconnect the horns and listen for the relay to click on and off. This will help you locate it. I have not checked but it will probaly be in the passenger kick panel which is about the hardest spot to access, as the plastic panel has to be unbolted to gain access to the relays. Once you have done it once it is easy. With the airbags just disconnect both battery negatives and wait for 90 seconds. I'd give it five minutes. I've never had one go off. Relays normally fail off but the contacts could be welded together. As you said the fuse was blown so maybe this was from a short circuit when your car was in for repair and has welded the contacts closed. 2K to repair a relay sounds like they didn't know what they were doing. The landcruiser dash is easy to access and takes about half an hour to almost totally disassemble it. Hopefully your theft ECU hasn't taken the short cicuit because this also fires your horns, but I would try the steering wheel horn switch which often jam on. Good luck.

 

[rdang]

I realize this is an old thread, I'm having the same problem - what is the P2 relay? I think I will give this a try first before I bring it in. A Toyota mechanic mentioned that I should be able to pull the factory alarm connects out of the main computer to disable the factory alarm which could be the root of my problems... anyone heard of this before?

Thanks guys.
Rick

i responded to someone's post a week or so ago with a similar problem. My 99's horn was going off on it's own. it turned out to be the P2(I think) relay which is somewhee near the dirver side foot. It was corroded. rather than relplace the relay($2K), the tech coated the relay with waterproof grease after scraping away the corrosion. That's been a couple of years ago now and it's still working fine.

 

[mmaakk]

I had the opposite problem where my LC horn worked intermittently and then stopped all together. The cause was a frayed wire underneath the airbag which is a coil that wraps around five times; there are special instructions on the install so I had the dealer do it(didn't want to mess with the airbag). Anyhow, it may be a short causing the opposite effect which is sticking your horn in the on position if wires are being crossed; cost was around $350 labor and parts. my 2 cents!