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Old 06-15-2012, 07:31 PM
fuji9740 fuji9740 is offline
Learning to use the forums
Join Date: Jun 2012
Posts: 10
Default Re: EGR Flow Insufficient (PO401)

I'm assuming you checked for carbon deposits in the barbs for the hoses connecting the DPFE to the EGR tube. Check continuity between the the wires between the computer and the DPFE and also between the computer and EGR solenoid. Make sure the pins in the connectors are good and tight too.


If that is okay then you would have to hook up a volt meter to the EGR solenoid to verify that the computer is commanding the EGR to open (and what voltages to look for I have no idea best guess is 5 volts D.C.) and to verify that that it is opening we would need to tee in a vacuum gauge at the egr valve to verify proper operation of the solenoid while driving. (This is the best way to run the test.)

So if our wires are okay, flow to the DPFE is good and, the computer is commanding the EGR sol to open the valve and vacuum is getting to the EGR valve, that leads us to two conclusions.

1. Aftermarket DPFE is bad, install factory part. DPFE's are always bad with a P0401.
2. PCM is bad and isn't reading what the DPFE is telling it.

If still unsure/don't want to do all that work take it to a dealership. It will take them about 30 minuets to figure it out with the IDS scan tool.

Hope this helps.
97 extended cab 4.0 5 speed 4x4 31 M/T warn manual lockers where it matters. Fancy black euro tail lights and a nice stereo for fun.
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