'96 taurus problem code P0402?

My check engine light has been coming on & off for a while so yesterday i took it to Autozone to have it checked. The code is P0402...It states "The PCM has determined that there is excessive flow in the exhaust gas recirculation system." what does this mean? i dont want to take it to a shop only to have to pay for diagnosis & then repairs :shakehead . Can anyone help?

Simply replace the DPFE sensor to repair the problem. Also inspect the 2 small hoses that go to it for any cracks or leaks.

i'll see if that fixes the problem. Thanks!