Lincoln/Mercury Repair: Emission, ckt, trouble code

Question
My mechanic got a code from testing the Emission:
CKT - what does this mean?  

Answer
Hi Anita,

Ask your tech for the code number. Also, please supply me with the year and model of the vehicle. Thank you!

Follow up:

There is no Diagnostic Trouble Code with CKT in it. We are looking for a number that looks like P0755 or P1711 or hundreds of others that start with "P". Emission testing will not help us.

Hi Anita,

You know, I was thinking of your delema today and realized the CKT means circuit. So he has part of the code we need. If you could please get the code number I will gladly tell what circuit is failing!