Ford has had problems with the wiring harness between the PCM and the COP. They have issued out a Special Service Message (SSM) for this problem.
"Confirmed Fix ** Running a new wire from pin 26 of the PCM to #1 COP fixed the problem. This is a copy of the text taken off of Ford's web site: 2001-2003 ESCAPE 3.0L - INTERMITTENT MIL ILLUMINATION AND/OR DTC P0301 OR P0351 SOME 2001-2003 ESCAPES WITH THE 3.0L DURATEC ENGINE MAY EXHIBIT AN INTERMITTENT MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATION AND/OR DIAGNOSTIC TROUBLE CODE (DTC) P0301 OR P0351. IF NORMAL SERVICE DIAGNOSTICS FAIL TO ISOLATE THE ROOT CAUSE, CHECK FOR THE POSSIBILITY OF DAMAGED WIRING IN THE 12A522 HARNESS AT THE 104-PIN POWERTRAIN CONTROL MODULE (PCM) CONNECTOR. CHECK FOR DAMAGE TO THE LIGHT GREEN/WHITE CIRCUIT 1024, PIN 26 AT THE PCM CONNECTOR. LOOK FOR SIGNS OF DAMAGE AT THE FEMALE TERMINAL OR TO THE WIRING INSULATION. SERVICE AS REQUIRED. REFER TO THE 2001 ESCAPE WIRING DIAGRAM SECTION 303-07B-00 FOR ALL MODEL YEARS "