I've had this problem since the first key fob battery needed changing 3 years ago. Since then I've had to renew the battery about 10 times. It is not the key fob battery at fault, it's something in the car. My wife also has a key fob to my car and she has the same problem with it. I've changed her battery half a dozen times. Sometimes it operates the door locks perfectly, sometimes it just doesn't work. Sometimes the doors open OK but then I can't start the car because the presence of the key fob had not been recognised - "SMART KEY NOT FOUND". If this happens, I've learned by experience that if I press the key fob to LOCK the doors, they will lock, then I can start the car and then UNLOCK the doors. Other times, I get the "Smart key battery low" warning come on whilst I'm driving, the if I stop the engine, start up again, the chances are that the warning has cleared. This is driving me mad - any clues please?

 

Subscribing to this thread. I have one key fob that the previous owner used exclusively that went "flakey" in December, just as you describe. Changed battery when the car said it was low and that only made it worse. The other key fob that is "like new" works perfectly and I have been using it since. Just have not had time to get it checked out - maybe when I take it in for the airbag recall.

 

Firstly, I'm very grateful for your reply Phil. The trouble is that I have exactly the same situation with my wife's key fob (to my car). Surely they both can't be faulty? Do you think that the receiver module might be faulty, and, if it is, is there an easy way I can get this checked out at the Jaguar place where I first bought the car, without letting myself in for big bucks?

With best regards

Silver cat

 

You wouldn't think that both key fobs would go bad at the same time. What are the odds? But since I've got the same symptoms with only one fob, then I was thinking you might just have a statistical anomaly. On the plus side, surely it would be easier and cheaper to just replace the key fobs than to replace any modules within the car itself. Unfortunately, I have no idea where the relevant computer module or components are located within the car.

I just figured that my one fob had just been worn out. Its pretty beat. Even all the chrome had flaked off the side trim and you can barely read the markings on the buttons anymore. The spare fob was probably never used until I needed to switch.

 

Hi Phil, thanks for your reply. I think I'll try and have a non-committal conversation with the local Jag franchise. The trouble today is that most of the fault finding is driven by a computer flow chart and most rectification involves changing expensive modules. The last car I had was a Mercedes E-class; I took it in to the Merc centre because I had a red hydraulic system warning on the dash. They followed the computer algorithm and then told me I needed a new hydraulic pump, so I applied a bit of amateur common sense - then found that the problem was an intermittent open circuit on the alarm! I saved about £800 and had no repeat of the problem.

Happy days!

 

same issue here. bought car 15 months ago with one fob. worked with very poor range. starts the car and such, but ..

changed battery. even tries the hack or using to batteries of same diameter but half thickness to double the effective voltage...

bought a new fob from dealer for big $$

no real improvements.

no problem starting the car and no problem unlocking when grabbing exterior handle.

tons of problems unlocking or locking the car from ranges of 3 feet or more. yes, 3 feet!

the longest distance I've ever had success re: the car recognizing a lock or unlock command was from about 15'. that was one time...

another oddity is when i have the key fob in my pocket and i exit the car / close the door. It's definitely no longer in the car and when i press the button on exterior door handle to lock it, it beeps twice as if to indicate I've left the key in the car.. dunno why as there's no way it's sensing the key in the car, right? the only thing i can possibly think of here is that there is an original keyfob in the car somewhere??? remember, i only was given one fob when i purchased the car. this is unlikely / a long shot, i understand, but maybe??

or as another poster said, there is a receiver that is bad. i think i read or was given info that the car has multiple receivers for such signal. that makes sense with the door and trunk access given upon approach of either, right?

would love to hear ideas and info as it's discovered.

 

Hi Adam,

Interesting similarities - I still think it's a problem with the receiver module. I think you're right in that the car has multiple receivers and, come to think of it, I've never had an issue with the boot lock facility, which must operate a different receiver module. I'll have a word with the Jag merchant and let you know what they say....

 

I think it is doing the opposite actually. Mine does the same if I stand too far away from the door when I push the button so I think it is trying to tell you that you have pressed the button but it can't detect your fob.

 

One of my remotes was doing the same thing. I rebuilt it, didnt change the battery, but i did flex the metal tines up so that they press harder onto the battery surface, seems to have fixed the problem.

 

Kaeghi, I'll give it a try - thanks for your insight!

 

Just thought I'd post a follow up. I finally took some time to tinker with the faulty fob. Opened it up, cleaned and carefully spread the contacts, particularly the tiny one that makes contact with the positive rim of the battery, so that they make a firmer contact. It appears the battery is held firm in a recess within the plastic body, the circuit board seems to have a little more freedom to float within the body so every time you push a button, its flexing the battery terminal contacts ever so slightly. Over time, they bend and weaken. Before reassembling the unit, I also peeled off the remaining chrome flakes from the side trims and spray painted them gloss black. The repaired fob seems to be working fine now. Thanks.

 

Thanks buddy - what you did makes sense and worth a try.

 

the part number for just he chrome fob sides is c2p15136, the part number for the cover with the buttons is c2p15135.
You can search Ebay for Jaguar remote smart key rebuild xf
26.95.

 

Hi Kaeghl, many thanks for this information!

 

Watch out for the eBay non genuine oem ones. They are cheap but not a perfect fit. The chrome edges don't quite fit on the OEM plastic case at least on the one I tried, and the plastic case that came with it which they did fit seemed cheap and didn't have the Jag logo on it. So I stuck with my existing one...