So here's a new one. Had my car washed today and when I went to go pick it up, the horn came on and just stayed on. There were cars all around, so it took me a while to realize it was me. I pull over to the next parking lot, and the horn stays on even after shutting off the car. Seems to go off with locking the key fob, but as soon as I start the car up again, it goes on until I mess with the fob again. But ultimately, I can't get it to shut off when the car is on, so I just pulled the fuse. I hear all sorts of chattering around the fuse box, so I'm guessing there's a bad relay somewhere. With the fuse pulled, the horn is at least off, but now I have a "Adaptive Dynamics Fault" showing up after pulling the fuse. I'm about to go on a long trip, so no time to investigate further for now, but curious to see if anyone has some experience or insight on what could be going on. Thanks in advance for any help.

 

How old is the battery - might be better to pull the relay - it's probably illegal to drive without a horn.

 

Did they detail the car? With the doors open there is a constant drain on the battery. It could be your battery is getting old (cause of many weird faults) and the drain on the batt may have caused the issues. At least give it a good charge to see if that clears the adaptive fault.

 

Could the panic button on the key fob be stuck on? Maybe try another fob.
And checking/charging the car battery is another cheap thing to try.

 

The sign of a failing battery on these cars, meaning almost fully discharged, is the horn sounding and often accompanied by the lights flashing. The last gasps of life.

 

Simon,

I agree with everyone that said it's the battery. I have some additional thoughts.

You can try charging your battery with a real battery charger with at least 10 amps. Amperage is the measurement of the flow of electrical current - think of amps like a speedometer for electricity; how fast it's charging.

Most battery maintainers are 4 or 5 amps, which is too slow to charge a dead battery; trickle chargers are 1 or 2 amps.

Once a battery is fully discharged, it will never be able to hold a full charge. How long it will last thereafter is a crapshoot. I would replace that battery now, instead of risking being stranded. Just make sure that your new battery is fully charged before it's installed, since many brand new batteries sit on retailers' shelves for months discharging before they're sold.

Your Public Profile shows that you have a 2013 XKR, which has the Battery Monitoring System Module attached to the negative battery terminal. It doesn't have to be reset by a dealer using SDD as it will eventually relearn the charging profiles while you drive.

Or you can have your Jaguar dealer do it and have the peace of mind that it was done right and have a warranty. They'll also test the charging system and inspect the rest of your car. It's not cheap, but might be worth it to you.

Stuart

 

Thanks for all the feedback. I've been through the unexpected weirdness of a dying battery before and replaced the battery a couple years back. Admittedly, I moved the car out of the garage last year, so I haven't kept it hooked to my CTEK like I used to, but the reason I'm a little skeptical it's a battery issue is that nothing else seemed erratic --the car started right up at the car wash, and then several times again as I fiddled with the key fob and fuse box. I'm personally leaning on the relay being bad. I'm traveling now, so if I come back to a completely dead car, then I guess that would confirm the bad battery theory. At any rate, taking out the fuse was the only option at the time given the horn was staying on full blast even with the car off.

 

I agree with this. BMS periodically goes into 'learn' mode where it discharges and recharges the battery to determine its characteristics. "BMS reset" simply forces BMS to go into learn mode now instead whenever it was next due to. Of course, I have no idea how often BMS re-learns or what factors other than time/mileage etc might determine the schedule. Forcing an immediate re-learn is necessary if you're changing the battery type/composition, but otherwise probably not.

 

Pulling the fuse was a smart move to silence the beast, but now dealing with that "Adaptive Dynamics Fault" message seems like adding insult to injury. Definitely sounds like there's some electrical gremlins at play there.

 

I'd say your hunch about a bad relay is probably spot-on. Those little guys can cause all sorts of mischief when they decide to go rogue. Hopefully, once you have some time to dig into it, it'll be a relatively easy fix.
And hey, speaking of fixes, I came across some interesting horn solutions at https://bosshorn.com. Might be worth a look.

 

Have you found any signs of water intrusion in the convertible boot area? There is a wealth of control modules and terminations in that trunk area just behind the rear seat. By now, I'm sure any evidence of moisture from a miss directed water stream is dried, but the damage to electronics would be lasting. Any OBD codes?

 

old thread but the front power box is wet