Forr the last 4 nights in a row the alarm on my 04 xjr has been going off for no reason Any idea of wats wrong

 

Could be a weak battery. Also do a hard boot for all the computers and see if that works.

 

How do you know it's for no reason? Maybe it's just a really stupid car thief that thinks he'll have better luck the next night.

 

I have a similar problem. How do you do hard boot for all the computers?

 

remove negative cable from battery, touch positive terminal for a sec. clears all memory and capacitors. thats the hard one.

 

I gave it a try. The problem happens 2-3 times a week so I'll have to wait and see if it does the trick! FYI I have a 2004 XJ8 and discovered that the problem is being caused by a false "Bonnet Open" alarm.

 

I get the "Bonnet Open" on my car every so often. I had the dealer look at it and they said everything checks out fine. When it happens I just open and re-close the bonnet with a hard slam. It doesn't re-occur until the bonnet is opened again.

 

Well that didn't work! The alarm went off again over the weekend!
I know its being caused by a false "bonnet open". I have tried opening the bonnet and slamming it shut but it still occurs. Anyone have any ideas???

 

My first thought was a bad switch on the bonnet (hood) so I tried opening it and slamming it shut but it doesn't clear the alarm display and I often get a "Bonnet Open" alarm while driving. If I could figure out where the switch was I'd try replacing it but I haven't been able to find it yet. It shouldn't be that difficult to find...anyone know where its located? Its a 2004 XJ8 VDP by the way.

 

I got it I remembered that i took my front bumper off to install a bigger innercooler. After reinstalling the front bumper i noticed the hood didnt line up. so i addjusted the hood. This cause my open bonnet light to come on from time to time after talking to a good reputable jag mechanic i found out that the bonnet light is wired with the alarm system. long story short I ajusted the bonnet switch (On the bottom part of the hood latch) and havent had the alarm go off for two nights

 

Found and replaced the "Under bonnet security switch" and so far things are looking good. Hopefully the problem is now resolved!