Does anyone know where the backup battery for the security system is located in a 1994 XJ12/XJ6?

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I don't know of a backup battery - if the security system has a keep-alive-memory, it may be powered by one or more capacitors built into the ECU.

I assume the system is similar to the one used on the '93 cars - you can see the schematic on pdf page 86:

Jaguar XJ40 Electrical Guide - 1993-1994

I don't recall a backup battery on the X300 security system either, but I may be wrong.

Cheers,

Don

 

This may be applicable. I'll have to look around under the dash to see if so:

https://forums.jag-lovers.com/t/xj40...ystem/250896/3


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That's an interesting thread, Al. Have you looked up the TSBs that Bob Gauff mentioned? I wonder if they might mention this elusive battery?

I thought it was interesting that highhopes said, "As far as I know nobody has ever seen the back-up battery on a '94
XJ40." I will be very curious to hear what you eventually learn on this topic.

Cheers,

Don

 

Looking at the electrical service manual, I don't see any mention of a backup battery either, so *shrug*

Isn't it interesting that the "Security ECU" has a connection to the antenna? I wonder if this is the radio antenna, or the in-car phone antenna, or?

 

I think this is one of the antennas in the backlight/rear windshield glass, but I don't know if it is shared with either the phone or radio.