EGR - P0401 Insufficient Flow

I'm at the end of my rope with my Duratech 3.0L 24V DOHC. I can reset the code and drive maybe a hundred miles over about 5 trips before it sets again.

Here's what I've tried. Changing the DPFE sensor, verified the EGR valve works, switched my EVR valve from my F150, verified all hoses & connectors look ok, and poured thru the search hits.

Any ideas on what to try next?

http://www.obd-codes.com/trouble_codes/generic/p0401-insufficient-exhaust-gas-recirculation-flow-egr.php
According to the web page, this is the way to fix it.

Are you referring to your 1999 Taurus?

Sounds like you did some very logical checks. Sounds like maybe you've already seen the following list. Have you verified power to the various sensors and made sure the sensors themselves are not open circuit (resistance check)?

Per the factory service manual, the following are possible causes:

-- Fault in vacuum supply to EGR vacuum regulator solenoid.
-- EGR valve stuck closed or iced.
-- EGR valve diaphragm leaks.
-- EGR valve or flow path restricted.
-- EGR vacuum hose off, plugged or leaks.
-- VPWR circuit open to EGR vacuum regulator solenoid.
-- EGRVR circuit to PCM open.
-- EGRVR circuit to PCM shorted to PWR.
-- Differential pressure feedback EGR (D.P.F. EGR) sensor pressure hoses both connected improperly.
-- D.P.F. EGR sensor pressure hoses reversed.
-- D.P.F. EGR sensor VREF circuit open.
-- Downstream pressure hose off.
-- Downstream pressure hose plugged.
-- Damaged orifice tube assembly.
-- Damaged EGR vacuum regulator solenoid.
-- Damaged D.P.F. EGR sensor.
-- Damaged PCM.

-Rod

I just used a NGS and pulled the following parameter off the vehicle. At idle and no EGR the PCM saw 1.05 V from the DPFE. At 3500 rpm, the DPFE saw about 0.15 V. These voltages are reversed. At idle, I should be getting 1V and at high rpm I should see an increasing voltage out of the DPFE sensor evident of positive EGR flow.

I must have switched the hoses when I installed the new DPFE.

Very good find, and thanks for the follow-up!

-Rod

Did you use an OEM DPFE? On the Windstar board aftermarket sensors seem to be junk.

I am having similar experience with 96 sable 3.0 tec.

I haven't checked voltage yet (haven'r figured out how to connect leads while engine running?)
on my DPFE the hoses are definitely different diameter - I don't think I could have reversed them?

Don