Hi,
Volvo XC60 2010 D3 2.0

I have a problem with the horn—it keeps honking continuously. I checked the fuse—it’s fine. I can’t find the relay; maybe this model year didn’t have one?

When I disconnected the horn, there was 12V on one pin of the connector and 0V on the other. Should it be like that?

 

The contact reel carries the signals from the steering wheel horn switches to the steering column module, then to the CEM which activates the horn relay. If you have 12v on one of the horn wires - the relay is closed for some reason. (probably not a bad stuck closed relay). The other wire at the horn goes to ground - so you will not find voltage on that one.

Possibly a bad contact reel - but should be properly diagnosed first. (contact reels are expensive)

 

Thanks for your reply.

The OBD shows error CEM-81C5513 – horn relay – open circuit.
Do you still think it’s not the relay?

I could try to test it, but I can’t even find it. It’s not under the hood and it’s not in the fuse box either. I have no idea where to look for it. In your diagram it’s shown under the wipers, but mine isn’t there.

If the clock spring (steering wheel contact reel) was damaged, would the computer also show error CEM-81C5513?

Should there be constant 12V on one of the wires in the connector? I don’t think so. The 12V should only appear when the horn button is pressed – am I right?

 

1. The contacts in the relay are spring loaded. When not energized a spring pulls the contacts apart. It's not likely the contacts have welded themselves together and are resisting the spring trying to un- contact them. So I think the relay is being energized - not from a bad relay - but from some other signal.
2. It's shown in the "cold zone". I don't have a car to look at but I would imagine that would be under the cowl between the windshield and the hood. The area where the wiper linkage is. It looks like the horn relay is the only item in the 15/33 "cold zone" box.
3. Don't know - I have not researched that code. Unplug the clock spring and see it the horn stops or unplug the horn buttons.
4. There should not be 12v on the grey/black wire at the horn. That means the relay is closed and sending power or the grey/black wire is shorted to power somewhere after the relay.

Why is the relay closed? Perhaps one of the 4 horns switches in the steering wheel is broken and in the closed position. Perhaps the clock spring is partially broken and the two horn wires are shorted together. Without VIDA or a fancy scan tool I would probably start by removing the airbag and checking horn contacts and the clock spring. Or just take out the fuse

If curious you can find these factory wiring diagrams for your car at volvodiag.com under the EWD tab.

 

I know the schematics almost by heart. I looked for that relay for so long that I eventually gave up — trust me, it’s simply not there
I removed the horn fuse and the horn stopped honking.

I think I’ll actually start with the steering wheel — I’ll disconnect the airbag and check whether the horn still honks.

 

I trust you know if you disconnect an airbag and turn the key on - a code will be set that requires a (not basic obd ) scan tool to erase

Can't find a better picture but below is what the horn relay is housed in -

 

I will disconnect the airbag with the battery disconnected. As I understand it, there’s no need to worry about any code then, right?

I can see your diagram, but I don’t have such a box under the hood. Maybe someone from the forum could take a photo of that relay?

 

1. You will only get a SRS code if you turn the key on (with the battery connected and the air bag unplugged)
2. Have you looked under the cowl cover (#1) as pictured below for the box/horn relay?

 

2. Yes I have looked

 

I just noticed in the 2010 supplement wiring diagram (maybe for cars built later in the year) - a couple of other relays are pictured in that box. (have not looked to see what r3 is)

 

In my case there is simply no relay box under the windshield The relays are located next to the fuses in the engine bay, in sections A, B, and C. However, these appear to be A/C-related and similar relays. I’m starting to wonder whether a horn relay even exists on the 2010 model year.