When I bought my X-Type the lock button on the key FOB worked but the other buttons did not. Only 1 key. The lock button stopped working soon after. I bought one of the cheap uncut keys with FOB from eBay. It came without the little security "pill" but I was just trying to get the FOB working. It did not work at all. Tearing down the old FOB I saw the old buttons were worn out, they did not click or even move much at all. I desoldered the buttons from the eBay FOB and transplanted them. Also transplanted the rubber membrane so the old FOB looks great and has a satisfying click feel to the buttons, but they still do absolutely nothing. I have tried the pairing sequence a few times and it does nothing. I have replaced FOB batteries so I know it isn't something that simple.

How do I figure out if the key is transmitting anything? How do I figure out if the car is receiving anything?

For clarity when I say the FOB is not working I am talking only about the 4 button remote that can be detached from the rest of the key as in the attached picture. The key blade and security transponder "pill" work fine.

 

You might try an AUTO PARTS STORE to see if they have a keyfob transmitter testing unit.

I bought a cheap one from Amazon and it works to tell me what (if any) frequency the transmitter is on.
Dead transmitters don't read on the device. (433 or 315)

 

Hey mate, its likely the remote is set for the wrong frequency, luckily as it's a clone remote it can be easily changed. Check it out here:

https://www.jaguarforums.com/forum/s...6/#post1818790

 

That is a great trick. It doesn't help my issue as my FOB is the same one that used to work with this car, I just transplanted the new buttons and the rubber pad. Unless I somehow managed that sequence of buttons and changed the frequency inadvertently. Worth a check. Thanks!

 

Wanted to circle back to close out my key FOB question in case anyone else has a similar problem. I ended up buying a $6 radio receiver tuned to 315 MHz, the US standard frequency for key FOBs:
https://www.sparkfun.com/products/10533

Apply 5 Volts DC to the power pin, ground to ground, add 6" of wire for an antenna, then connect a voltmeter between the analog out and ground. Measuring Volts AC I get about 0. Using any of the 4 non-Jag FOBs in the house gave about 1 to 1.5 V AC as soon as I press any FOB button. The voltmeter integrates different codes to different AC voltage. For the sake of this test the level is meaningless, just that it jumps from 0 to something with a working key FOB. FOB from previous owner did not work at all. New cheap-o eBay FOB did not work at all. I got out the soldering iron and the magnifying glass and found a bad solder joint on the eBay FOB. Resoldered it and tested, no joy. Look closely again and find another iffy solder joint. Fix that and suddenly I am transmitting signal. Opened the old, original FOB that I had soldered new tactile switches on and find the contact between battery and circuit board is bent and has some black carbon at the contact point. Clean up the contact patch, bend the little tabs, press a button...It lives! I was frustrated trying to sort out whether the FOB wasn't sending a signal, the car wasn't receiving, or something else. For $6 (plus shipping) on that receiver I was able to verify the FOBs were not sending out any signal and modify and test them until they did.