Security light blinks car won't start disconnected the battery used a different key still won't start

I don't believe there is a problem either.
Under normal conditions the security light should come on then go off if the correct key is being used.
The problem could be the key switch or the neutral safety switch if it is an automatic trans. There are other possible causes.

the problem you have is caused by the pats anti theft system is not recognising your key it may be the transponder or you may need a new key and get it programmed by a jag dealer or someone with the needed gear to do it with best advise take it to a jag dealer

Very interesting site here.. regarding your problem. http://vatspasslockpasskeysecurityhelp.yolasite.com/
Another thought.. even though you charged the battery, it's not at all uncommon for a car battery to be very damaged by fully discharging. Especially if not new-ish. One or more cells in it may be bad causing the overall voltage to be under normal. This alone can cause the problem you have. I would try jumping it with another car or test the battery to see if it's got at least 12.7 to 12.9 volts when sitting doing nothing. Good luck.

spare key may be a valet key and will not turn off security, try locking the doors and using the key in outside lock -unlock, or unlock and hold, double tap. play with it a bit each manufacture makes there own little tricks, good luck

is the security light lit? try a different key to start.
if no start do the following.
try to start car then let go of key do not turn it off.
wait 15 min for security light to go out.
turn key off wait 5 seconds then try to start again.

the passkey system is not the best design, a little wear on the key and it won't start, if the tumbler wears out it won't start.

the system is either hooked to the battery or it has a fuse try disconnecting them

Is the security light on or blinking?If not then do you have power to the starter.You can check this with a test light.You should have power when you turn the key to start.The test light should light up.Should be the small wire.I believe it is purple in color.If the security light is on then you will have to get the codes to see what is causing the no start.Hope this helps.Good luck.

check battery volts should be 12.6 volts battery either weak,or battery cables could be loose or battery cables and post has corrossion clean corrossion from both cables and post using small steel brush clean battery post with.first turn off radio before disconnecting negative battery cable.

If the security light is blinking, then the security system is DEFINATELY the reason why your car won't start. The actual cause of the problem is MOST LIKELY a defective ignition switch that is not sending the information from your key to the computer.

Try this:

FIRST try a different key if you have more than one for the vehicle. I have had cars towed into my shop simply because someone was trying to use a cheap duplicate key that was cut at the hardware store. These keys are fine for the doors and trunk. They are great to have around in case you lock your keys in your car. However, they do not have the electronics built into them to allow for engine starting.

If you are using the correct key and a second key also does not work. then...
1. set your parking brake (this will disable your daytime running lamps and conserve battery power.)
2. Connect a battery charger to the vehicle battery if you have one, or see if someone can connect to your battery with jumper cables.
3. Turn the ignition to the START position for about one second. Then release the key to the RUN position. DO NOT turn the ignition OFF.
4. Wait about 10 minutes until the security light quits flashing. Turn the key (without turning it off) to the START position again. The engine should start. If it does not, then you will have to get your car towed in for service.

HINT: you may want to try this a couple times to make sure you are doing it correctly before towing.

If it does start, it is recommended that you have your security system checked for fault codes. I have seen this many times, and it only gets worse and does it more often until this method no longer works to get it started.

If any of the gauges are blinking and going haywire and the security light flashing then the instument cluster is faulty.But if it is just the security light flashing then its in the switch.If you only had the switch replaced then you need a new ignition lock cylinder because its worn out.