My 2007 Jaguar XKR 4.2 alarm has started to go off for no apparent reason. I've had the car from new, it has just had its 110K service and this has never happened before.

I lock the car by double pressing the door handle button. The alarm is random with no obvious reason.

Any idea what might be causing this issue. Coincidentally, my wife's X5 recently had a similar issue and disconnecting the bonnet sensor seemed to fix it. Is it likely to be a similar issue with the XKR?

I had a look under the bonnet but couldn't easily identify any alarm sensors/connectors.

 

Your battery is probably low. Yes, I know this will not make sense to you but the XK depends on full voltage all the time; the car will always start even when the battery is low. When the voltage drops the XK will start to show random and odd electronic issues - and the problem is always the battery not being fully charged. Many people therefore use a battery maintainer (CTEK being the preferred brand). Result: zero problems. You might have a different issue, but I doubt it.

 

+1 on vehicle battery being most likely the cause. If the battery is the original one, replace it and save yourself from problems such as what you have, which can be quite vexing.

 

The battery was replaced in November 2013, so is less than 3 years old. I checked the voltage yesterday and it looks fine, so I don't believe it is the battery. Also, it false alarms during the day, not just at night when the air temperature is cooler and is more likely to affect low voltage batteries.
sov211, unlike many Jag owners, my car is driven 50 miles every week day, so there is no need to "maintain" the battery.
The next best option seems to be the bonnet switch causing the issue. Googling suggests this is an issue that affects many cars, but I'm not seeing any reports specifically for the Jaguar XK. Also, I'm not getting any warnings to say the bonnet is open.
Does anyone know how to change the bonnet switch? There are many instructions/videos of how to do this for a BMW X5, but I can't find anything for a Jaguar XKR, which maybe suggests it is NOT a common issue.

 

Don't know what info it tells you or if this applies to your X150 because the TSB doesn't have a VIN range but it is for X150's and XF's:

INFORMATION ONLY

Concern:
It has become evident that some dealers are unaware that the last alarm trigger data is displayed on the HLDF screen.

This can be used to diagnose alarm concerns in a quick and efficient manner.
Action:
To read the last alarm trigger data from the HLDF screen follow the instructions below:
• Enter the vehicle and turn ignition on.
• Press "Vehicle" soft tab on the HLDF screen.
• Press "Vehicle Settings" soft tab.
• Scroll down using arrow.
• Last alarm trigger will be displayed in a grey tab at top right of HLDF screen.
Note:
• Only the most recent trigger will be displayed.
• XK only – Alarm trigger history is also available via IDS if required.

 

Hi u102768,

Thanks for that most useful information. I followed the directions and it says the alarm was triggered by the volumetric sensor. I remember reading about issues with this and XK owners getting them changed under warranty. Unfortunately at 8 years old my XKR is a long way out of warranty
I believe there are two of these fitted and one of them is trickly to get to.

Out of interest, anyone know what causes things like sensors to fail? I assume they have no moving parts and they are installed in inaccessible areas that protect them, so why would a volumetric sensor suddenly (after 8 years) start to cause false alarms? Is it due to the quality of the materials used or built in redundancy?

Interestingly, or coincidentally, the false alarms only started last week, the 2nd night that I parked my car on the drive, rather than in the garage. Usually, the car is always in the garage, but I currently have a project that takes up too much space to allow the car to fit. Given that I live in England, and despite it being almost May, we are still getting some very cold weather (in't North)! Maybe she is just complaining that she is cold

 

2008 Jaguar 4.2 alarm going off all time I lock the doors with the remote control. Hi can anybody assist with this matter. If I switch the allarm off on the display and look the doors, the allarm will go on and when I check the display it says allarm on. The only way is to look the car with the key, but then it useless to have a remote control and the alarm might working in case of need. Maybe reset all the car, taking off the battery for many hours, I am trying now. Thanks for any suggestion.

 

I had a somewhat similar problem years ago, turned out that the Boot Latch was out of adjustment.

 

Thanks and how did you get it fixed? Thanks

 

I gave it a wonk with a rubber mallet. Seriously. Haven't had a problem since.