2002 Mercury Cougar 2.5L V6: P1401 and P1406 Error Codes Explained - Fix with DPFE Sensor Replacement
I own a 2002 Mercury Cougar with a 2.5L V6 engine, currently at 76,000 miles. My OBD-II code reader is showing two error codes: P1401 (EGR Evp) and P1406 (High Voltage). I'm trying to understand what these mean. I notice the car runs smoothly with no idle issues or hesitation—only a slight drop in fuel efficiency of about 1–2 MPG. My assumption is that if the EGR valve were stuck, the engine would run lean and exhibit performance problems. However, this isn't happening. The only noticeable change is reduced mileage. I've already checked the vacuum lines connected to the EGR valve—these appear clear and respond properly when suction is applied. I also tested the EGR valve itself under vacuum, and it functions normally without sticking. My question: Could a clogged exhaust tube downstream from the EGR valve (the one connecting to the bottom of the EGR) be causing P1406? Are there known cases where such lines become blocked on Mercury Cougars or other Ford-based vehicles? Any insights, troubleshooting steps, or common fixes would be greatly appreciated. Eric
Check the throttle body ports and vacuum hoses, as well as the DPFE (Differential Pressure Feedback EGR) sensor—this is a very common issue on many Ford vehicles. Once you've inspected those components, please update us with your findings.