Hi All...

We own a 1998 X308 (XJ8) with around 76,000 miles

it's my understanding that the electronics can be reset by connecting the negative battery cable to the positive terminal for a not yet specified period of time....
i, while not completely mechanically proficient, have quite a bit of experience with working on my own vehicles...but this is our first Jaguar.

What would happen if this was done???

to be quite honest, when i think about performing the battery cable "trick", i start to get cold sweats, my heart-rate increases, my hands shake violently and i feel a migraine (possible aneurysm) begin...it seems to go against ANY logic...and yet i've heard several opinions on what will happen....one being that it will fix some of the strange electrical events that were not present when we purchased the kitty...

Thank you all in advance for your help...i have been very impressed with the knowledge that many of you offer newbie enthusiasts....

Sincerely,
JagsNHarmony

 

There's nothing to it, but you always want to be cautious around batteries. The safest way to do this is disconnect the negative lead first (This way if your wrench accidently touches the metal of the body, nothing will happen).
Then remove the positive lead (with the negative lead removed first, it's ok if your wrench touches the car).
Then hold the two leads together for 10-30 seconds (I'm guessing a bit here) and hook them up again, positive first, negative second.
NOTE: Do NOT close the trunk with the battery disconnected, countless owners, including myself, have found the key mechanism is often stuck from never being used, and with the battery unhooked, the electric release doesn't work.


EDIT: you can leave the leads touching for as long as you want, no harm done, but at least 30 seconds I'd say. This does cure some ills, on lots of cars, not just Jags. Are you trying to fix something specific? Be ready, it may idle funny for the first minute after you do this trick, again, no harm done.


DO NOT UNDER ANY CIRCUMSTANCES CONNECT SOMETHING ACROSS THE LEADS WHILE THEY ARE STILL ON THE BATTERY. Sorry to yell, but I just want to be perfectly clear, both leads must be disconnected first.

 

All that happens is the capacitors in the various modules discharge and effectively wipes their memory.

The same thing will happen if you just disconnected the battery and left it for a while.

Once done, any memory functions you have on the car will need to be reset including the radio code, if your car requires one.

So in short, no need to sweat, but what problems are you having? Perhaps some one here could help.

 

Yeah. I have measured the voltage with the leads diconnected and after 30 seconds or so, there is NO measureable voltage. No voltage, no difference!
I usually touch the battery leads together anyway when I do the "hard boot" ... to feel good about myself having done something!

 

[/QUOTE] Sorry to yell, but I just want to be perfectly clear, both leads must be disconnected first.[/QUOTE]

i would MUCH rather be "yelled" at than to do something stupid that can and will cause more problems than already present....Thank you VERY much for your advise....sounds pretty straight forward and i'm hopeful that some of the issues will subside....{really just need to kinda "start from scratch" so i can isolate what seem to be random issues that did not happen when we first got the car, ie; windows rolling down at will, mirrors moving on their own, etc.


again Rob, Thank you for your help....it is much appreciated!

 

You're welcome! While you're at it, do some reading on the forum, search for threads on battery cables, false bulkhead, and the engine ground strap. These cars have a few little problem areas, and when all the cables are sound, and the battery is healthy, they're great cars. Weak batteries or loose or corroded cables cause all sorts of strange behavior.

 

I've done the "hard reset" on my 2003 XJ8 many times. My mechanic got cold sweats the first time I did it in front of him!

I simply remove the negative cable and touch it to the positive post for a minute or two. After doing so, the car will act differently when driven until it gets re-acquainted with you! There's a procedure somewhere around here that tells you what to do after re-connecting the battery, but I don't have a link to it right now. Just remember that you could get idle surges and erratic idling for a while after re-connecting the battery. Just drive it normally until everything settles down, that should work just fine.

As for the window and mirror issues that you have, I agree that you should at least try a hard reset first, you just never know what'll get fixed by doing that. But, you might have an issue that requires a bit more expertise to fix. Good luck and let us know how the hard reset works for you.

 

TSB 1-186
Read the bottom of page 7 for Jaguar's recommended battery reset.

bob gauff