I was in a bind with a 2008 XJ that only had 1 key and FOB. Ordered 2 brand new keys/FOBS off EBay.
Got the Jaguar dealer to cut the metal blanks. This is required BEFORE you attempt to program the keys! Glads it was only $21 to cut the 2 blanks. Just a boat load of paper work because you have to prove it's your car to the dealership!! Copy of the title and my drivers license were required.

What this gives you is a key that will go into the ignition and turn the power on in the car BUT you won't be able to operate the starter. If you try it just operates the ignition switch and nothing happens.

My main confusion was how SDD defines the keys. With only 1 key you run into a problem because everywhere I read said you need 2 working keys.
This is true but they DON'T need to be programmed! Just blank is fine with a valid transponder installed in them. Then when faced with the SDD options you want to "Program New Transponder".
Selecting this will get you to erase ALL keys. This is necessary so you can start all over from scratch. Note that this option will ONLY get you 2 working keys.

Now you can follow the SDD to get 2 keys operating which worked fine but there is a 30 second time limit so have everything you need before you press "continue". But I wanted to have 3 complete keys working. So next you follow "Program Additional Transponders". This DOES need 2 completely operational/programmed keys to work. Again follow what the SDD screen says and now you are in a 5 second window and it took me at least 4-5 times to complete it in the allotted time! Just a whole lot of key switching on and off plus removing and swapping keys. It's a bit frantic but don't worry because at this point you can't really screw anything up but merely need to go thru the cycle again.

As most people know programming the FOB section that unlocks the doors and trunk can be done 2 ways. I use the SDD as it was fast and easy to do the FOBS.

Very happy and glad I read the mountains of threads out there on SDD and all the programming. Saved a lot of money as the only local locksmith I could find quoted $400 to start!!
Not too hard but as always the SDD is NOT a user friendly system and there are NO training or troubleshooting things to help you.

My key things for a SDD are;
Proper DC power unit. I got a used Iota DLS-55 for around $100 after I repaired the leads and plugs.
I use a Mangoose clone cable with Drew Tech Pro drivers.
Running Win 7 64 bit PRO on a dedicated laptop. No Virtual machines. I am on the internet and currently running SDD 157.06. Still applying updates with no problems. I did leave the machine off the network for several weeks and got a nag about updating SDD or you would get reduced functions. Not real sure if this will continue and I am considering running a "Deep Freeze" type program to stop that as I have read there is a 7 or 14 day timer in the system that will always look for updates. I could find no way inside SDD to stopping updates.

But ALWAYS make sure your battery symbol is green and that the Mangoose is connected to the SDD!



I have circled the 2 symbols to watch. Note this is using my old battery charger and I only got a yellow battery symbol. I did not do anything other than look around. I performed no functions until I got the green battery symbol.
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Get two keys, with chips programmed, and your ready to program the rest yourself.

 

Key Fob / Remote
Key_fob_facts_all_you_need_to_know
Program Key Fob Instructions #1
Program Key Fob Instructions #2

 

The problem/confusion is there are 2 separate functions?

The FOB is to unlock the car.
The transponder is to start the car.
They are both integrated into the flip key.

The FOBS are easily done by anyone. Programming the transponders is much more difficult and involved.
My main problem (and why I posted) is only having one working key. If this is the case you have a very dangerous operation because the SDD requires wiping ALL keys and starting over if you don't have 2 working keys.
So if there is a failure during this operation you now have a car that has no keys and will not start!
It's not the end of the world because you can attempt to program the transponders again but you still may have some sort of failure and will need to tow the car to Jaguar.

Even if you have no working keys at all you still can use the SDD to program the transponders to the car. But you MUST get a key that will mechanically go into the ignition switch and turn. It will not start the car at this point.
You can get the key code to cut the blank from the VIN of your car. Jaguar will NOT give you this unless you can prove ownership. This required me to provide a copy of the title and my drivers license. I had one working key at that time and wanted 2 more blanks cut to match.

Maybe a lock smith would not require this but I spent at least a month calling around to see if anyone could do it. I got promises and costs of $400+!! Jaguar cut the blanks for $10 each.

This method will allow someone to steal a car if they can get the key code. Newer Jaguars ( I think 2015 and up?) have changed this making it much more difficult to add or reprogram transponders.
It is now required to change out the KVM module or sometimes another module called a RFA (Remote Function Actuator) because they are only programmable once and are locked from then on. I am not sure if you can buy the module without proof of ownership or not?

Here is a discussion of the new requirements on a UK forum.

Lost Key Replacement
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You are going to have to get two keys,
Then have them programmed to your Jaguar.
All the other keys out there, are now unable to start your car.
Then have at least one more, in case you loose one.
My 07 Jaguar had only one key, with no remote.
I had a couple remotes from a wrecked Jaguar.
Used keys are available cheap on ebay.
I bought a lot of used ones from a locksmith there.
Local locksmith cut my needed keys for a of couple of working Chinese remotes.
That the key portion, would not accept programming, but the remotes would.
Got my money back from seller, they didn't want the keys back.
Pulled the metal key part out to be cut after installing them into my remotes.
I now have plenty of working keys, for not a lot of money.