Good morning all.
Please could someone enlighten me! My 2010 X351 has recently decided to emit a single car alarm sounding chirp at regular four hour intervals. There are no other obvious symptoms.
I’d be most grateful for any words of wisdom.
Dan.

 

The chirp is an audible warning of an electrical fault. How do you determine exactly what's wrong? Most electrical problems are caused by a weak battery. So ...

The first thing I would do is check the condition of your battery in the morning, after your car has sat overnight and before you start the engine. If your battery reads less than 12.6 volts, replace it with a new AGM battery that has been fully charged before installation. I got my OEM battery replaced at Pep Boys with a Bosch AGM for much less than my dealer charges, and am pleased with it. See: https://www.jaguarforums.com/forum/x...attery-212478/

Another factor is how often you drive your XJ and for how long? The Pandemic has caused many of us to stay home and not drive very often. That will cause your battery to run down and weaken to the point of causing a wide variety of electrical glitches. All the computer modules in the X351 require a minimum voltage to properly function. To keep your battery fully charged, I recommend that you install a CTEK or other quality battery maintainer. See:
https://www.jaguarforums.com/forum/x...lation-130801/

Typically, the sounder beeps to indicate that a door/hood/trunk is open, you've already locked the doors, the Smartkey battery is low, etc., together with a warning light on the dash.

If no warning lights are lit up to tell you there is an issue, then you will want to get the Diagnostic Trouble Codes (DTCs) from the OBDII port. You can do this yourself with an inexpensive ELM327 scanner and the free Torque app for your Smartphone. Hopefully, the DTCs will tell you what system is detecting an electrical issue. Otherwise, you will have to manually test these components with a voltmeter to make sure the input and output signals are reading correctly.

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Sincere thanks Stuart for a brilliantly comprehensive reply. Your car usage assertion relating to Covid related lockdowns is 100% correct, which has likely contributed to the deterioration of the battery.
Armed with your wisdom, I’ll be able to have a far more educated conversation with my trusted local mechanic.
Thanks so much again for your generous sharing.
Dan.

 

Dan, you may find it helpful to simply take your car out for a 30 minute drive every week. This should be enough time to get the battery back up to 100% and it also allows you to get out of the house to not go stir crazy. You do not necessarily need to stop anywhere. Just cruise a country road and see the views. Doing it around sunset is always a treat. Ironically, letting a car sit for long periods of time is very hard on them. Go figure.

 

I agree and did a 80 mile cruise today just for fun.
Had a wonderful mild sunny day so it was just a pleasure to drive the XJR.
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.

 

I am curious. I have a CTEK charger. Once my car has achieved full charge, and is in the mode where it just keeps it topped off, my XJ alarm will go off about every 1 hour. I solved the problem by just leaving it unlocked. I was wondering if any other CTEK users have had this issue. It was an easy solution, but if I lived anywhere but the UAE, it probably wouldn't really be a viable one.

 

sgtm7,

Leaving the doors unlocked is not a solution. Your car has an electrical fault and it's only going to get worse.

I suspect that your battery is weak and should be replaced. By leaving the doors unlocked, the computer modules never shut down; your CTEK keeps charging continuously and never stays in maintenance mode. It's fooling you into believing your battery is healthy when it's not.

Have you checked the condition of your battery with a voltmeter like I recommended in my Post #1? If not, do it the morning, after your car has sat overnight and before you start the engine. If your battery reads less than 12.6 volts, replace it with a new AGM battery that has been fully charged before installation.

Most electrical gremlins are caused by a weak battery.

 

The battery is less than 18 months old. I have previously measured directly at the battery, and the voltage is good. I checked the voltage, not because I had any issues, but because I routinely check things on my cars. The only reason I even bought the CTEK, is in case I take a vacation longer than 12 days. I know when being away for 12 days or less, it starts right up with no problems. I hooked up the CTEK to check its operation, because I plan on the first vacation I take(once travel restrictions are lifted) being a long one. It could be some kind of electrical problem, but if so, it is weird that the alarm going off when in the CTEK maintenance mode is the ONLY symptom.