DPFE Sensor...Code 327 on 1995 Ford Contour...

My sisters 1995 Ford Contour recently started stalling and acting up. A shadetree mechanic told her it was the EGR Valve.
I cleaned her EGR valve + passages and checked the PCM for codes and
got just a code 327. Code 327 is apparently caused by too low of a voltage signal at the DPFE sensor.
One quick question: If low voltage corresponds with a closed EGR valve, and high voltage equals an open EGR valve, how can the valve itself possibly cause a Code 327 and therefore too low of a voltage signal?? In other words, how can an EGR valve be TOO far closed?? I can understand a carboned-up EGR valve not seating all the way, but wouldn't that result in the DPFE sensor seeing a voltage that is too HIGH and not too LOW??
I'm just trying to figure out how I figure out whether the problem is the DPFE sensor, or the EGR valve itself.
Does anyone have any recommendations on where to start?
THANKS!:)
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The DPFE output has an 'offset'. With zero flow (actually zero pressure drop across the EGR tube orifice) it does not output zero volts. Depending on the model, it's either 0.55V or 1.0 V. Obviously, the purpose of this offset is to help the PCM figure out whether the EGR valve is not closing, or there is an electrical malfunction. So get a voltmeter, identify the wires and take a reading. A reading of zero is certainly a defective DPFE. But a positive reading still does not tell you that the sensor is working. When mine failed it was reading maximum flow. The sure way to tell is to hook a handheld vacuum pump to the intake manifold side of the sensor and see it responding to change in vacuum.

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bigbossfan80 wrote:

its probably that the valve is not too closed, but that the passage behing the EGR valve that lets the gases go to the intake manifold and into the throttle body are being blocked and insufficent... throttle body had to be removed an the EGR valve removed and the gunk behing the throttle body gasket cleaned out .... go to: www.contour.org and ask for info on cleaning out the gunk from the throttle body to EGR valve and see what you get there.. hope this helps.
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it's very common to replace a DPFE sensor on a ford. some of them were even updated over the years. Chip
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snipped-for-privacy@yahoo.ca says...

Usually the voltage out of range code is caused by failure of the sensor. These are pretty common failure, especially in cold weather. Seems like a little moisture can migrate into the sensor, freeze and bust the thing. I had to replace this on my Taurus the first winter I had it.

Process of elimination. Check the associated hoses and wiring first, then the sensor is relatively cheap and easy to replace. If you have to replace the EGR valve, a fresh sensor may be a good idea anyway.
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