What you are trying to do here is to check the voltage output of the DPFE sensor. Initially it should read around .45 - .55 volts or .8 - 1.0 volts @ KOEO, depending on the application (that's because DPFE sensors will have either a 0.55 voltage offset or 1.0 voltage offset). Use the table below for guidance, but you should check to be sure which offset is used by your vehicle's DPFE sensor:

Aluminum Housing

(0.55 voltage offset)

Aluminum or Black Plastic Housing

(1.0 voltage offset)

- Continental
- 5.0L Explorer/Mountaineer
- 4.6L F-Series and Expedition
- 4.6L E-Series

- All Others

1. Make sure the Key is ON and the Engine is OFF (KOEO);

2. The wire harness remains plugged into the DPFE sensor for this test;

3. Check DPFE SIG for .45 - .55 volts or .8 - 1.0 volts (as per the above table);

4. If DPFE SIG at KOEO is not within the indicated range, then the sensor is faulty and should be replaced;

5. If the KOEO voltage is OK, start the engine (KOER) and put a vacuum pump/gauge on the EGR valve hose port:

(a) If increasing the pressure (hence opening the valve) does not cause the engine to run rough, then there is probably some blockage in the system. Check the EGR tube ports, the EGR Valve orifice opening and vacuum port, and the DPFE sensor hose ports and hoses, and make sure that none of these are coked up with carbon.

(b) If increasing the pressure does not cause the DPFE SIG voltage to rise, then the DPFE sensor is probably at fault.

6. Next, test the voltage output of the DPFE sensor at different vacuum levels (KOER). Apply varying amounts of vacuum to the downstream port (intake side) of the DPFE sensor and monitor the voltage at the DPFE signal line. The amount of voltage should correspond to the level of vacuum as shown in the graphs below: