Electrical Gremlins.

[Spannerdemon]

Hi

Hoping somebody can help my daughter out here. I live in the NE of England and she's in Devon, so I can't just pop round! But she's got a problem, and I'd be grateful if anyone has had this same issue and can help.

Here's what she sent me.... It's a 2014 Toyota Yaris.

My car is poorly ��
Yesterday on my way to work, my horn suddenly came on constantly which was entertaining! It stopped with the ignition off but when I left, it came on again as soon as my lights came on. I took the fuse out for the horn just to get home.
Anyway. We went to go out earlier and she was dead ��
Had to call green flag who have been out. It seems to be a fault with the lights as my headlights stay on even with everything off. He's disconnected the horn and put the fuse back but I'll have to take it to Toyota. I can drive it, but he's disconnected the battery so I'll have to connect/disconnect each time I drive it ��
I'll ring them Monday as typically there's no one in service today ��

She REALLY needs this working for her job... Can anyone suggest what might be the problem. I'm thinking maybe a dodgy relay or similar but I'm not familiar with Toyotas.

Thanks if you can help.

[CoryM]

My money is on an aftermarket alarm/immobilizer. Remove it and you're probably good to go.

[B.B._07]

I second that, an aftermarket alarm or remote starter will tie into both the horn and signal lights circuit. The horn and headlights are on separate circuits so a problem with one won't usually affect the other. Even if you don't have a aftermarket alarm or starter I'd take a look at the wiring under the steering column.

[Spannerdemon]

Thanks for this guys. The car packed up completely yesterday, and has now been taken to the main dealers as it's still within its warranty.
As far as I am aware, the car is factory standard, so the only alarm/immobiliser fitted will be tge Toyota one.
I'll post again once it has been to the workshop, and my daughter gets back to me, but thank you for your kind help, which is appreciated.

[Spannerdemon]

Ok. The update is that the dealership couldn't find any fault and so have returned the car to my daughter.

I can't say I'm convinced by this at all. She certainly didn't imagine the problem and it did the same thing the following day.

So it looks like it's one of these intermittant things that are such a cow to find. The lights have mysteriously gone out again and the horn is behaving.... Nothing found to rectify.

My best personal bet is that it's a relay. I've had this before with a fuel injector relay myself. Car just stops. Nothing to see. Despite being returned for diagnosis starts mmediately then runs fine for 2 days, then same thing.Complete fuel failure at 70mph. Breakdown people out, car starts first time. This time runs for 3 weeks.

A tip I read advised taking out the (in my case, fuel) relay and giving it a sharp tap. This frees off the sticking contacts within the relay and all is well..... Until the next time.

In this case replacement of the relay solved the problem permanently.

But two dealers, 4 garages and an auto electrician ALL couldn't find it because being intermittant, basically there was nothing to find.

I suspect and half expect a similar outcome.....

[09GLH]

I had an issue with the ground point behind the battery on my 09. 2 dealerships and 3 transmission shops couldn't diagnose a bad ground. I had to weld up the hole and buy a new OEM ground cable, been right as rain since. I think I posted on here about it somewhere...

[jra]

If she has a key fob with a panic button on it, could be the problem? Could be the horn and lights share a ground some where that's corroded so when the lights come on they ground through the horn setting it off? But, as others have said, most likely something with the alarm system.

[DarkShadowFox]

i pull up on my up on my window up button and my headlights dim, with the window all the way up, is that normal?