I Have 2002 Focus Wagon with about 146000km, I suspect the DPFE Sensor is going bad (Deteriorating mileage and mid range missfire, but no codes are being set) so to test I unplugged the DPFE sensor, engine response and power improved and mileage seems to have picked up to, what is confussing is the the PCM is not setting a code or pending code that the sensor is disconnected or failed and the PCM has been cycle though a couple of dozen start stop cycles and travel about 750km. Anyone have an ideas why the PCM is not detecting the sensor circuit open. The same sensor failed recently on my 96 Sable wagon and the MIL light came on instantly if the sensor was unplugged. I am going to replae the sensor anyway just wonder why no code is set.

 

yes should of came on but a dpfe wont cause a misfire,have you changed your plugs 146 000 your due

 

Thanks, no doubt the plugs could use a change, I assume they are originals, I bought the car used in the summer.

When the DPFE sensor starts to fail, it provides bad information to the PCM and causes the the PCM to open the EGR valve to much, this leans out the fuel mixture with the recycled exhaust causing the engine to stumble, this typically occur when cuising at highway speed up hills where slight trottle application is required. When I unplugged the sensor these syptoms disappeared, tells me the sensor (which area known issue for pretty much every Ford that uses them) is the culprit, a missfire due to spark plugs should result in a flashing MIL and would also set pending and stored codes indicating the cyclinder at fault, but nothing is being set in the PCM.