Hi all , i have a 2001 XJ with all the usuall mods , anyway i was tucked up in bed the other night & out of no where the XJ's just starts sounding non stop , the only way to stop was to pull the leads off the horn , & when i started her , 2 seconds later she shut down mmmmmm tried again samething mmmmm tried again & all good hooked up the horn wires & still all good , shut her down & re-start i have a yellow key in a circle in the top left hand corner of the dash , start her up again & she shuts down , key light blinking , some times it starts with no trouble & other times i get the 2 second shut down in the end i pulled the horn relay out to stop it blowing its own horn lol all fuses check out okay , i have no shorts or bad earths that i can find , any thoughts on this weird behaviour , Sentry key reader failing , key failing , anyone else had a similar problem with there XJ's im at a loss as where to look next when everything seems okay , i even pulled the stearing wheel off & checked all the contacts & wiring running through the column , nothing its all good HHHEEELLLLPPPPP lol

 

Sounds like a security system gone awry.

 

New one on me... wish I could help... subscribed to learn the outcome so when u fix it post up so I know man lol... good luck!

 

my tj did that once. been fine ever since.
next time, maybe disconnect the battery to reset any codes?

 

security systems will do a 2 second run then shut off, i would check there first

 

x2 on this... never seen something this wild happen but from what you have described it is most likely the security system from the factory...

 

I would check the wires that are hooked up to the ignition, make sure its plugged in and not cut anywhere, you can also bypass this system if need be by installing the right resistance resistor in the wire from the ignition switch

 

Ill post the cure when i work it out , so far im thinking the ignition barrel has a part to play in it , dose this make sence to anyone , if ii get a clean release when shutting down everything is okay , but if i just jiggle & pull the ignition is not fully off , so there is power stilll running through the switch , but the factory sentry imobilizer system cant read the key because its not there or in range of the reader so it tricks the system into thinking its being tammpered with so it sets the horn blaring , dose that sound fesable or am i reading to much into it lol

 

could be possible, i would replace the ignition switch, purly because by messing with it you can make it work or not. i think your switch is grounding itself out inside depending on how you move it, and making the computer think someone is trying to start it

 

This is going to sound dumb.

after you have everything connected back(horn, whatever else)
with the driver door open lock it from the inside.
Shut the door.
from the outside unlock, lock, and unlock with the key.
this should tell the security system everything is ok.

This happens to my wife all the time, usually when she locks the door with the remote before the door is closed.

Or when the battery dies.

Hope it helps. And if u already did this sorry for the post.

 

I think your alarm system may have lost its last nut

 

No need to be sorry mate ill try anything to rectify this X-File & yep ur right it could well have lost its nuts lol anyway im over playin with cars today so ill get back into the xj over the weekend & let you all know what happens , cheers for the help everyone