Trouble Codes
Postmaster
Joined: Oct 2009
Posts: 3,432
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The P1443 can be due to either a bad purge solenoid, or a bad purge flow sensor.
A code P0401 most likely means one or more of the following has happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve
And the P0171
A code P0171 may mean that one or more of the following has happened:
The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor.
Possible Solutions
Possible solutions include:
In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure
All three codes can be caused by vacuum leaks.
A code P0401 most likely means one or more of the following has happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions
In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.
Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve
And the P0171
A code P0171 may mean that one or more of the following has happened:
The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor.
Possible Solutions
Possible solutions include:
In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure
All three codes can be caused by vacuum leaks.
Thread Starter
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Junior User
Joined: Mar 2010
Posts: 50
Likes: 0
Wow! Thanks for that info! 
My MAF is brand new, how do I know if my air filter is oiled or not? It is brand new also and I didn't check the box.
I will check the hoses out after this T-Storm passes. If hoses check out could I try putting in some SeaFoam?
Also, there is a hose connected to the large intake hose leading to the oil filler tube. Is that a vacuum hose as well? It is metal with spongy like end connectors. I remember that connector being worn and I wrapped electrical tape around it.
http://i182.photobucket.com/albums/x.../underhood.jpg
My MAF is brand new, how do I know if my air filter is oiled or not? It is brand new also and I didn't check the box.
I will check the hoses out after this T-Storm passes. If hoses check out could I try putting in some SeaFoam?
Also, there is a hose connected to the large intake hose leading to the oil filler tube. Is that a vacuum hose as well? It is metal with spongy like end connectors. I remember that connector being worn and I wrapped electrical tape around it.
http://i182.photobucket.com/albums/x.../underhood.jpg
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