Moved the Jag out of the garage to use the space to work on the house. Place to cut lumber etc... It has been on a battery tender all winter and the battery is a bit over a year old. After sitting for about 2 weeks I went to open the trunk and it wouldn't open. Battery DEAD! How can this be? What if I drove it to the airport and went on vacation for a few weeks? Come back to a car that won't start? 🤦*♂️

 

Check the little "Door" that covers the Ignition Key Slot to make sure it closes when the Key is removed. If it sticks open, the Security System will draw more Current and could run the battery down

 

Maybe . . . maybe not . . . what was the actual battery voltage that you measured to make such a pronouncement? Wouldn't be the first that saw QCD drain a battery (PATS advice is a known cause) and if so, you need to perform QCD analysis (see Sticky How To in S-Type forum) but . . . also could be a fob tx/rx issue. Did you use key to open door? Was car then suffering flat battery or did it suddenly "wake up" and react normally?

Cheers,

Ken

 

I opened the trunk with the key and put the tender back on then walked away. Oh and I disconnect the negative terminal.

 

So . . . maybe the battery wasn't dead . . . likely, but not proven, and only a DVM measurement of standing battery voltage is diagnostic. Please believe my concern is to make sure you get the correct diagnosis . . . and if your car has a PATS issue, it will almost certainly recur despite the battery tender.

Best wishes,

Ken

 

Well I assumed the battery was dead when the trunk wouldn't open with the button. Didn't want to open the doors because the glass wouldn't drop if I tried.
I've been having many issues along the same lines for over a year. Most of them fixed temporary with a hard restart.

 

Mine goes into a deep sleep after a couple of weeks, which means the remote unlocking and boot button don't work. Try unlocking the door with the key and with a bit of luck it will come back to life.

 

That interesting. I'll hook the battery back up and see what happens.

 

Exactly . . . and well put. Most do precisely the same and is commonly reported after 2-3 weeks sleep. I hesitate to coin the term "hibernation" rather than just "sleeping" but your trick of key opening works every time . . . followed by normal resumption of the lock/unlock functions. Moreover, this longer term "hibernation" is totally unaffected by whether or not a battery tender is connected.

That's why pronouncing the battery good, sick, bad, or dead is meaningless. The only reliable diagnostic is the measured standing battery voltage (<12.6V invites trouble) or, to be technically correct, also the measured cold cranking amperage (CCA) which dictates not just that the battery can crank and "start" the engine, but still have sufficient voltage headroom to successfully "start & run" all the car's electronics.

If we seem to bang on endlessly about this . . . well, you need the local auto shop to measure CCA, but spending $5-$10 for a DVM to DIY measure battery voltage is a no-brainer compared to the cost of a new battery.

Best wishes,

Ken

 

very interesting same thing happened to my 01 xk8 , key fob did not unlock boot or disarm security , but after opening boot with key everything worked as if nothing had happened, is this normal or just a glitch?

 

Hi Jeremy. Quick answer . . . normal if Jag has been hibernating for at least a week or more; abnormal if wanting to drive back home after a day's work.

As to whether this "hibernation" is normal or a "glitch" I have spent considerable time researching TSBs and all available manuals & docs re PATS. All I can point to are numerous posts reporting same here, usually as an initially assumed fault, and our shared experience on UK and ROW Jaguars of all models across that era, as confirmed previously . . . consistent and predictable. Perhaps it is also common on US/CAN imports? Perhaps not?

Cheers,

Ken