If you've not seen it, you can remove old keys from the PATS system with two known good keys ( no clones ), just like you can add them. The procedure is fairly simple, but must be done correctly.

In adding keys, you put key A in, wait three seconds ( I count five dings of the key in lock chime ), remove A and put B in for the three seconds. Now you're in program mode and can add keys C, D, E, ...

The procedure for removing all the old keys is similar. Put keys A & B in as if you were adding keys, then put key B in for the three seconds, then finally key A.

NOTE: THE SEQUENCE MUST BE A - B - B - A !!!!!

Found out the hard way that if you do it A - B - A - B it clears the B key and you have to go to the dealership or locksmith to get the B key put back in to allow you to do more adding of keys. The sequence starts and ends with the A key. By going A - B - A - B the system cuts off after the second insertion of the A key and virtually ignores the second insertion of the B key.

The only exception to this is vehicles equipped with remote start. The PATS system will recognize the remote as an A key and your physical key as a B. That goes for adding keys as well.

This might be a good one for a sticky so no one else accidentally clears their keys