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Troublecode p0401
1999 Mercury Cougar

Troublecode p0401

(1999 Mercury Cougar)
I cleaned out the ports to the egr and replaced the egr and light still came back on. What else could it be?
2 answers & 0 comments
Popular Answer
on January 23, 2009
You'll want to test the DPFE sensor and EVR solenoid for proper function as they are the primary sensors/control for the EGR valve. The Differential Pressure Feedback EGR (DPFE) Sensor may be sending false data signal to the PCM. Direct linking does not work but Autozone's site has repair guides for your Cougar that do say how to test the DPFE and EVR.
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800a8aa6
Select your car and follow the link to "Drivability & Emissions", then "Emission Controls", and finally "Exhaust Gas Recirc..". It says how to test the components.
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General Diagnosis
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on January 23, 2009
You'll want to test the DPFE sensor and EVR solenoid for proper function as they are the primary sensors/control for the EGR valve. The Differential Pressure Feedback EGR (DPFE) Sensor may be sending false data signal to the PCM. Direct linking does not work but Autozone's site has repair guides for your Cougar that do say how to test the DPFE and EVR.
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800a8aa6
Select your car and follow the link to "Drivability & Emissions", then "Emission Controls", and finally "Exhaust Gas Recirc..". It says how to test the components.
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on March 21, 2009
Also check your spark plugs for misfires, I think the egr systems flows off of a spark plug, I have a 95 Mercury cougar and and my egr sensor was bad, I replaced it and the two other sensor that go with it, and then relized that on my 4.6 v8 engine spark plug # 6 was not firing so I changed all the spark plugs and wires and now my car run great.
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