P0401 -- Exhaust Gas Recirculation Flow Insufficient Detected <<< what does this mean?

I got the above code on my 99 Taurus, does it mean the EGR valve is clogged and needs replacing. Or isn't it quite that simple?
Comments welcome. Here's the rest of the codes involved with the
Exhaust Gas Recirculation...
P0400 -- Exhaust Gas Recirculation Flow Malfunction P0401 -- Exhaust Gas Recirculation Flow Insufficient Detected P0402 -- Exhaust Gas Recirculation Flow Excessive Detected P0403 -- Exhaust Gas Recirculation Flow Circuit Malfunction P0404 -- Exhaust Gas Recirculation Flow Circuit Range/Performance P0405 -- Exhaust Gas Recirculation Flow Sensor A Circuit Low P0406 -- Exhaust Gas Recirculation Flow Sensor A Circuit High P0407 -- Exhaust Gas Recirculation Flow Sensor B Circuit Low P0408 -- Exhaust Gas Recirculation Flow Sensor B Circuit High P0409 -- Exhaust Gas Recirculation Flow Sensor "A" Circuit
Thanks,
Norm
PS I reset this code for the moment. Three weeks ago I had an O2 sensor code (P1131), which I also reset, and so far (knock on wood) it hasn't returned or even been pending yet.
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Probably needs cleaning at the least. This includes the ENTIRE system.. from exhaust to intake egr port

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wrote:

The most common problem with those is the DPFE sensor which may give several of your codes.
Lugnut
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There was a major recall on the DPFE sensor for many Ford & Mercury models 2000 and above, not sure if any 99 model years were covered. I would suspect the DPFE, had it happen to my wife's 2000 Taurus wagon twice. First was replaced under recall, second I had to do. Part costs about $30 and takes five minutes to replace on the Taurus. Small hands help because it is located between the firewall and the engine, at least it is on the DOHC Duratec.
You might be able to tell if the sensor is bad by checking the DPFEGR pin on the sensor. Remove the wire harness from the sensor. Looking at the pins locate the top or left pin (depending on your engine it might be different). With the key on and engine off check the voltage to that pin. From what I am reading if it is between 4 and 6 volts the sensor is bad.
I say "might" because I've never actually performed this test. This I got from interpreting one of the pin-point tests I have for my 2000 Taurus DOHC. However, if I am in error you count on someone spotting it and offering additional advice and maybe even a few choice words for general entertainment.
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P0401 almost always seems to require a DPFE sensor replacement. It worked for mine a few months back. Replacing it also, IMO, removed the "jerkiness" from the engine on acceleration.
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Thanks everybody for your thoughts and ideas!
Norm
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