Had this same problem with my 2014 Jag 2.2 XF, went to my local garage who read the error as a plug/seal needed replacing, cost me £50, you can buy readers but before you get any further damage I'd certainly have it read first.
Hi
I have been on ebay recently and seen a number on their site about £40 - £50, depends on the model of course, but you should find one there.
or
There is always jagbreakers.net
https://jagbreakers.net/part/2/58/715/xf-range/lighting-exterior-interior/rear-lights/
Regards
Graham
I was recently contacted by my dealer to do the cambelt on my 2.2 xf diesel with a price of 550, had it done with the water with 2 other belts at my local garage I've used for years for 350.
Note here the car had done 43k and was 7 years old, the 7 years old triggered it.