Hey there!

So we all know that Jaguars are temperamental. I refer to mine as Dame Judy, and she is very stubborn at times. Anyway, I have a much bigger post for my on-going electrical problems which I will post another time, but first I would like to know if any of you XJ8 owners have experiences this new little gem that started yesterday. The battery had gone flat overnight (Remember the bigger post to come!!) and I boosted it with my eliminator box (very handy and now a permanent resident of the boot. I ran the car for a while to get the battery charged up and then shut it off and restarted; this normally resets the myriad electrical faults that appear after a flat battery. Here is the new piece to this... after this time, the fob(s) will no longer lock or open the locks. Both have new batteries in the fobs. I managed yesterday to run the car for a while, and did all the procedures that the car was requesting (degrees footbrake and apply parking brake to name one...) and following a restart the fobs worked again, but today, neither work.

Any ideas would be greatly received. More on Judy later... Cheers!!

 

It sounds like you need new battery. You can bring battery to any automotive store and they bench test for free.

 

Thanks for the response. The battery is new. As of today (after a few hour+ drives) it starts first time, and there are no warnings. With that said, the fobs still do not do anything. It's quirky.

 

You could try re programming the fobs using the headlight flashing method.
You have to flash really quickly to get it to work.

 

Interesting!

Is there a known situation that cause the fob/car connection to be lost?

 

Interestingly you can also get a key problem with the Rover 75 due to main battery problems. If you try to start the car too many times with a battery that does not quite have enough power to crank the car the ignition just clicks when you try to start it. If you do this too many times then the key fob looses connection to the car and you have to get the keys reprogrammed. I'd presume the Jaguar issue is caused in a similar way.

 

You are completely correct!

I did a quick search of the forum to find out the procedure for reprogramming the fob(s) and it worked like a charm. One thing that I did notice is that you have to flash the lights relatively slowly to activate the programming (there is an audible quiet horn sound). Once activated each press of the fob button resulted in another beep. I have attached the file that I found below. Interestingly I had previously noted that on occasion, when I removed the key from the ignition, I had heard the same beep (two quick beeps actually).

Anyway. One less thing to worry about. These cars have so much character... I can't stay mad at Dame Judy XJ8.

 

You were bang-on!. Thanks for the tip.

 

Glad to have helped Leslie.

 

Back to the battery, is it holding its charge?

If not, with a new battery, alternator comes to mind.

Quick way to diagnose if so, take neg cable off when setting any length of time.

 

Age of the battery is immaterial. Just because a battery is 'new' doesn't mean it's fully charged. Most often they sit on a shelf in a parts house and are not fully charged. A failing or weak battery can cause random DTCs to be set and other electrical 'gremlins' to appear. Many of the posts about electrical faults on these forums can ultimately be tracked down to the battery.

With the ignition in the OFF position for at least fifteen minutes, check the voltage across the battery terminals. It should be a minimum of 12.6 volts, if not, disconnect the battery from the vehicle and charge it at 5 to 10 amps overnight and retest it the following day. If the battery is still producing less than 12.6 volts, it should be replaced. A battery tender is not to be mistaken for a battery charger.

 

Age is a non factor, thats a certainty!!!

Believed the battery was new, fully charged, with the alternator charging.

Did not, & do not know, if our cars let you know, when a bad diode allows current bleed through.