Ut oh … Well, my fob, after working for two days following its re-programming, didn’t work at all when I went to use it for the first time this a.m… It did have two 2016 batteries in it, so hopefully I didn’t blow it up. Only other possibilities are (1) the batteries went dead (they were out of an old X-300 fob that I haven’t used in ages) or (2) somehow the fob became un-programmed again. 
(I really wish Jaguar would have preserved the green/red check LEDs of the X-300 fobs on the X-308 fobs, so we can tell if they’re transmitting, have juice, etc.)
MY BAD!!!
I took my X308 (99 XJ8) keybob transmitter apart and TWO 2016 batteries fell out!!!
The X308 and X100 need TWO 2016 (6V) to operate!! Just like the X300.
The newer cars (X200,X202,X400,X350etc.) need the single 2032.
Sorry but the older I get, The older I get!!!
Don’t hate me??
bob
Paul,
You can check to see if the remote is working by going to any Autozone or Advance. They have the tester to use for free! Just push a button on your remote & the tester will blink if the remote is good.
Richard
You had me going there for a bit, Bob, as my Driver’s Handbook clearly specifies TWO 2016s. I was beginning to wonder if I had the wrong handbook for my car (although the illustrations in it all seemed to match Harlem). 
btw, I put two fresh 2016s in my fob this a.m. and she works fine once again. Phew!
2 Likes
Good news!
Congrats.
Good to hear. I was prompted to use the ‘HEART’ button. I guess that is a LIKE button?
bob
Long time in getting back to you. You are indeed correct. All three transmitters had the wrong batteries in them. Once I switched them out I was successful in reprograming the unit.
Cheers