Not sure if I am in the right area, but, if not, please redirect. Thanks.
Problem: My husband had taken the car out for a little run while I was away to British Columbia; got back to bad news! The car worked great. Then on father's day, he and his sons went for a little drive, came back, parked the car. My husband got into the car again, and it wouldn't start; but the lights, etc were working according to his son. Then he locked the car, and when he went to unlock it did not. So my problem is, how do I get into my locked XJ8 Vanden Plas, since the keyless remote does not unlock the doors, and we now think the battery has lost its charge. Any suggestions beside breaking a window. If I change the battery in the remote, will it be able to unlock the door? I realize I will have to reprogramme the remote. Also, we did buy a car battery in October 2018. If we do get into the car, we know we have to recharge the battery. Many thanks for help, and please excuse the long message. shekellorie

 

I've moved your question from General Tech Help to X308 forum. Members here with the same model will be able to help.

Graham

 

Surely the simple answer is to use the actual key in the drivers door to access the interior of the car, or similarly use the actual key to open the trunk and access the car's battery?

 

Good Morning Carnival Kid: Thanks for replying. I had completely forgot about the key entry on the driver's door, thanks for the reminder, and I did unlock the car. But, I tried to unlock the trunk and the key did not work. So, I guess I'll have to the usual way I do when I come back from Florida, and then recharge the battery. I believe there is something draining the battery, and will have to have it checked, do you have any suggestions before I take it to an shop? The nearest Jaguar dealer to me is in Halifax, and I don't think it would make it. So, any suggestions would be greatly appreciated. Lorraine

 

Because the key is rarely used to unlock the trunk the internal mechanism often gets stuck, a squirt or two of WD40 in the key hole and some back and forth wiggling with the key often manages to free up the mechanism sufficiently for the lid to open.

The trunk will open using the key even with a flat battery, but it has to be the black headed key, not the green valet key.

 

What helps further is to press the trunk firmly down as you turn the key. It is much easier to move the latch.

 

Editing

The trunk can be opened if you drill a small hole behind the licence plate and use a round shafted screwdriver to lever the linkage over

Looking for a pic that shows this

This is a picture of someone that went too far but shows the mechinium you will lever though a small hole to open




On the earlier X300 version of your X308 you can charge the battery from under the front hood

The battery drain or parasitic drain can be broken down into sections

A common problem and easy to try is the ignition switch as you remove the key makes a switch to start the shutdown or go to sleep mode and keeps the battery alive and draining

key barrel lubrication help s to unstick this switch

 

A few observations.
As said above, you can put 12V on the system from under the bonnet, enough to open the boot, either with the remote or with the dashboard switch. Recharging a flat battery this way is not recommended.
You do not need to reprogramme the remote after replacing the fob battery.
You can test for power drains by testing amperage across each fuse. Remove the fuse and test between fuse and earth. Some systems will use a small amount when the car isn't running, but larger currents indicate a problem in that circuit.

If it were me, I'd start by testing the battery itself. I had similar symptoms with a battery that was just two years old. Replacing the battery solved that.

 

A +1 to the other suggestions and to add to them... check the terminals for corrosion...any corrosion, replace the terminal wire, you'll never get it cleaned properly again. Check for swelling on the battery, I've seen a battery test good but have a swell in it and it subsequently died shortly thereafter. Feel the side of the battery before charging (it should be cool to the touch) and see if it feels warm, it almost assuredly is bad or you have a short.

 

Good Evening Carnival Kid: I did get the trunk unlocked. As you said, it was stubborn and I had to move it around. I am now recharging the battery. Once again, thanks.

 

Thanks, I will remember this tip. These things always help.

 

Thank you for your information - it is interesting. I did not know there was a sleep mode - I know when I close my laptop it goes into a sleep mode rather than shutting down, so I am presuming this is the same idea. I'm looking over the diagram, but I do not under the abbreviations, etc. Would it be possible for you to explain this further, it would be appreciated. Thanks.

 

I did eventually got into the car, removed the dead battery and put it on a charge. I purchased the battery in May, 2019, so something is definitely draining the battery.

It would probably be a long process to test each and every fuse, and at the moment, I am not into doing this at the moment. Do you need special equipment for the fuse testing, if so, what?

Thanks for your help.

 

Thanks for your info. I did not know the information you gave me. At the moment, the battery is recharging and hopefully the Jag will start.

The info with regard to the battery is always good to know, so I have printed it and put in my file.

Thanks again.