The Delta Pressure Feedback exhaust gas return sensor is an emissions-related sensor utilised by Ford in many models such as the Focus, Crown Victoria and F-150 that monitors exhaust pressure changes. If your car is running poorly, and the check engine light indicates a EGR system failure, the DPFE should be checked, as it is a common failure source. While you will typically need to replace the sensor due to failure, you can clean it in an attempt to restore performance.
Open the bonnet and locate the DPFE. The location of the DPFE varies by engine. To help locate the DPFE, follow the metal EGR pipe off the exhaust manifold until two small tubes branch off. Follow those two small tubes to the DPFE. Some cars will have a large saucer-shaped vacuum hose attached to the top of the DPFE. On a Ford Focus, for example, it is in the centre of the rear firewall.
Use a 10mm socket to remove the two bolts that secure the DPFE to the firewall, then use needle-nose pliers to remove the two metal lines from the EGR system. Unplug the sensor, and then remove the DPFE from the stock location.
Check the EGR inputs to make sure they are clear of debris. Use electrical contact cleaner to clean the power input on the DPFE, making sure the terminals are clean of corrosion. Use a bit of electrical grade lubricant to cover the terminals. Clean the car's power connector the DPFE.
Re-install the DPFE by sliding the two plugs into the EGR tubes, then reconnecting the two 10mm bolts. Re-connect the electrical plug. Test to see if the car now runs like normal. If the car continues to run poorly, consider replacing the DPFE with a new sensor, as it is a well known failure point.
The DFPE will fail over time due to the fact that it is a sensor in a plastic housing, which is exposed to exhaust gas. The heat of the exhaust gas damages the sensor and the plastic housing over time. You can purchase a new DPFE at your local Ford dealership or from a local automotive parts supply store.