My wife just bought a 2001 V6 Mustang Automatic. She was getting a check engine light and she had it checked. They told her it was an EGR valve. So I bought a new one and threw on it today. While doing this I cleaned the Mass Air Sensor, the TB, and the IAC. Then I reset the computer and we drove it to town. Everything seemed fine. The surging idle was gone and it seemed to be much better. We went to eat. When we come back out as soon as my wife started the car we got a check engine light that stayed on. We went to Autozone and they scanned it. I was told both codes have to do with the ECM and that the computer may be going bad. I disagreed so I came home and did some searching. The P1401 turns out to be a DPFE sensor which is the EGR valve position sensor. I plan to drop another $30 and just buy the sensor and see what happens. I assume this is still the same code that she had before and I was just given bad info and replaced the valve when I should have replaced the sensor. Is there a way to test this sensor? The other code is P1000. Definition OBDII monitor testing not completed. Probable Cause: Codes cleared or battery disconnected.