Code P0401
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Code P0401
I have a 1997 Ford Explorer XLT 4.0L. The check engine lite recently came on and its giving me the code P0401 I know it has some thing to do with the EGR. I need help on how to trouble shoot this. The vehicle seems to run fine it will idle rough when first started for about 2 seconds it feels like the engine is shaking the whole vehicle. Thanks in advance for any help.
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Joined: Aug 2004
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As you know the P0401 code is EGR for insufficient EGR flow.
* Inspect the associated vacuum lines
* Inspect electrical connectors
* DPFE (Differential Pressure Feedback EGR) – Most likely and common problem. Probably gunked up inside. Measure the two terminals with a volt meter and with the
connector still plugged on and with the engine running. The Voltage should be between 0.35 to 0.8 volts with Engine running (cold) and 4.0 to 6.0 volts Engine running (warm). Warm is when the EGR is being requested by the PCM.
* EGR (Exhaust Gas Recirculation) – You can test the EGR valve by applying
vacuum to the EGR vacuum connection. This will open the EGR completely and
the engine rpm will decrease significantly or probably stall. This isn't a great test but should be sufficient.
* EVR = EGR Vacuum Regulator - Not sure how to test.
* Inspect the associated vacuum lines
* Inspect electrical connectors
* DPFE (Differential Pressure Feedback EGR) – Most likely and common problem. Probably gunked up inside. Measure the two terminals with a volt meter and with the
connector still plugged on and with the engine running. The Voltage should be between 0.35 to 0.8 volts with Engine running (cold) and 4.0 to 6.0 volts Engine running (warm). Warm is when the EGR is being requested by the PCM.
* EGR (Exhaust Gas Recirculation) – You can test the EGR valve by applying
vacuum to the EGR vacuum connection. This will open the EGR completely and
the engine rpm will decrease significantly or probably stall. This isn't a great test but should be sufficient.
* EVR = EGR Vacuum Regulator - Not sure how to test.
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Joined: Aug 2003
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If you have a metal DPFE it is known to plug up. I had the same code on my 2000. I searched this site and decided to replaced the DPFE with a new plastic one, it was around 90.00 from the dealer 
. If you decide to replace it I highly recommend you get new rubber hoses as well, my old ones were cooked on so I had to cut them off.
. If you decide to replace it I highly recommend you get new rubber hoses as well, my old ones were cooked on so I had to cut them off.
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