catalyst efficiency below threshold, grand marquis 96

I had my grand marquis LS codes checked because the check engine light is continously on and engine runs at a little higher rpm than normal. The codes indicate that catalyst efficiency is below threshold. Does any one know where these catalyst efficiency sensors are located. Will cleaning these sensors help the check engine light go away?

come on guys.. somebody would know this one.

You will need to replace the cat on side code is for.sensors are working fine they set the light to tell you cat isn't.