My car won't start

Check battery voltage, it should be minimum 12.4. Check the battery cables for corrosion and make sure they're tight. If cables are ok, check voltage signal at the starter solenoid as you try to start it

An if that don't won't work

Assuming the theft system is not activated, then you keep going back til you find the problem. From there, you'll check if starter fuse is ok, check if starter relay is turning on til you get to ignition switch or chip on your key

Did you ever figure out what was wrong? I am having the same issue with my jag.

I lost my key to my 2002 jaguar and need to know how to start it

Jesse, It uses a transponder key. You need to get a locksmith or dealer to make and program the key.

About how much does it cost

You would have to contact them. I say about $200