spare key problem

[dtools]

2005 LS V8 gen 2
All of a sudden our spare ignition key does not work the car
It will lock/unlock/power down/up windows etc when inserted in the door BUT will not start the engine.
Attempt to start the car will illuminate all dashboard lights and the alarm red light will start to flash rapidly - waited for a while - flash code 15
Primary key works great - battery brand new and replaced a couple weeks ago.
Is there a DYI method to re-program the original key (with only one working at this point) ?
Other suggestions ?

 

[joegr]

Do you have anything else on the ring with that key?

A scan tool with the ability to put the car into secure mode is required to be able to program keys when you have only one working key. If you start this procedure, and your 2nd key is defective (it very probably is), then you will have no keys that will start the car until you buy a new 2nd key. (The working key(s) get erased when you start the procedure.)

 

[dtools]

Appreciated the quick reply
Already have tried the key on its own (removed it from the ring) - no luck I'm afraid.
Quite strange for a transponder key to have "partially" corrupted embedded code.
Now I wonder how long the other one will last......

 

[All2kool]

A scan tool with the ability to put the car into secure mode is required to be able to program keys when you have only one working key.

I found a locksmith that added a new key for $45 - but it took at least 6 quotes from others to find that price, which was about half the next lowest price.

 

[dtools]

I wonder if I can use the valet key as the second key in the programming sequence (as per page 153 in the owner's manual) to reprogram/refresh the failing one.
Has anyone ever done this with success ?

 

[joegr]

I wonder if I can use the valet key as the second key in the programming sequence ...

Yes, you can. It has the same PATS chip in it. The way it is cut is the only thing that makes it a valet key.

 

[All2kool]

I wonder if I can use the valet key as the second key in the programming sequence (as per page 153 in the owner's manual) to reprogram/refresh the failing one.
Has anyone ever done this with success ?

I would agree. IIRC, you can add new keys as long as you already have TWO WORKING keys, which it seems you do.

 

[dtools]

I'll try this approach and will post the results
Thank you again for the prompt replies