Is there a battery in the ignition key? I tried the spare key a couple of weeks ago and, although all the lights came on, the engine wouldn't fire. Then last night I went to fill up with petrol and the car wouldn't start with the 'master' key. I waited for a few seconds, tried again and it worked.

Not very reassuring! Anyone have any ideas/similar experience?

 

There's a battery in the fob for the remote door opening/alarm etc but not for the actual key itself.

The key does have a transponder chip which is programmed to the ignition. Has the spare key ever started the car? Is it the original? If not it may not be programmed to the car.

If it needs to be programmed a dealer can do it, but will charge, possibly a lot. Some key cutting places have a programming machine and are usually cheaper, in fact I found one who progarmmed a key for me for nothing.

Not sure why the master key hesitated.

 

I have the 3 keys for mine. 1 didn't work and did as you describe - lights on, dash power, etc, but no turnover. I took them to the dealer to reprogram. Like an idiot, I left the dealer (which was 1000) miles from my house without actually trying all of the keys. When I got home a different key didn't work. The one that originally didn't work now worked, and the one I had been using before the programming didn't work.
Long story longer, I think it may have something to do with the chip in your key and could need to be reprogrammed. If you start the car with a key that works, turn it off, and insert the key that doesn't it WILL start - provided its done immediately after the car was running. If you wait a few minutes, then the unprogrammed key will only key lights, etc.

 

All keys have to be present to program any one key. They aren't actually programming the key, they are programming the car. The codes on the RFID chips in the keys cannot be changed. When they program the car, they wipe out any codes that are already programmed in and then program in all of the keys that are present. If you left a key at home, then it won't start the car. You need to take all of the keys back to the dealer and have them do it over again. I'm surprised the dealer didn't tell you that.

 

I'm sure there's a dealer closer to Buffalo you can use...

I just looked. The one in Raleigh is only 619 miles from Buffalo. You should use them the next time you need a key programmed.

 

I thought they could be changed. I took my original working key, along with a non working, newly acquired, spare to a high street key cutter and he just stuck it in a machine and programmed it in about 10 seconds. He didn't go anywhere near the car and the key now works fine, so I assume that somehow the transponders can be re-programmed.

 

Yes, the keys can be cloned. The idea of car responding to different transponders in keys can have to do with different drivers. One key will activate all the memory settings in one position and another key will activate all the memory settings in another position, etc. Remotes can be the same way.

 

On a slight tangent, what's the deal with valet keys, how are they technically different?

Are they physically different or just a standard key programmed differently?

 

Valet keys are programmed the same as ignition keys,but they dont open the boot/trunk lock when car is in valet mode as they are cut at a different angle on the key tip

 

Transponders, codes, batteries, valet keys, master keys, programming... what an absolute mess!

Thans for your replies, anyway. I will try some of your solutions.

 

Hey, it worked! I tried the spare key - no response, as before. Turned the engine on with the master key, switched off and then retried the spare and, hey presto, it worked!!

Thank you so much for the tip. It was always a bit disconcerting to know that I only had one key.

 

Wait... so I can buy a spare key and program it myself simply by starting the car with the old key, turning it off, then starting the car with the new key? If that's correct, I'm going to go buy a valet key! I have two regular keys, but no valet key.

 

With mine, the second key will work immediately after shutting it off with the functioning key. But, then when you go to use it a minute or two later it won't work.

 

just to add... my valet key also will not unlock the glove compartment.

 

That's so that the "valet" can't just flip the switch and steal your goodies that are locked in the back.

 

Aww crap, you're right. I just tried the spare key 24h on and it doesn't work. Thanks for building our hopes up, Jaguar