I just installed a New Factory (AER mfg, Romeo Plant) 4.6 in my 1997 F150 after getting a head leak at 180K, as options I installed Shorty Headers (Pacesetter, I know, I know,,,cheap), and a BBK 75mm throttle, went ahead and replaced everything including ignition, DPTE Sensor, EGR Tube, Cleaned throttle adaptor (1 EGR port clogged with Carbon). After 400 Miles I have gotton TWO P401 codes. The EGR valve only has about 30K on it. I checked my hoses.

#1 - Coming off highway from 75 mph down to 20 mph (1/2 Tank gas)
#2 - Put pop-up camper in bed, and ran about 12 miles and code lit along with drive train error (blinking overdrive light)

I am not worried about the drive train error, I can fix that, probable need a new tranny anyway (shuddering, even after two torque converter flushes), But am perplexed by the P401 error,
IS IT THE HEADERS and the LOWER BACK PRESSURE ?
If so, how do I fix it ?

 

First make sure you have the hoses from the EGR tube going to the DPFE sensor routed correctly. If they are reversed you will set that code. Unless you are running open exhaust, there should be enough back pressure. Make sure all of the vaccum hoses are connected properly.

 

I ran the pacesetter headers on my 97 with the 4.6 and true dual flowmasters with no problem with codes. Shouldnt be a prob.

 

I dont know what kind of mileage you have on your truck but ....... sometimes clogged EGR passageways in the throttle body elbow can cause this. Sometimes a more restrictive exhaust will divert a sufficient amount of gases through the elbow even though there prtially clogged up. But going to a more free flowing exhaust will allow enough of the exhaust gases to bypass the clogged EGR passageways to throw a code.

It's a long shot but maybe those EGR passageways need cleaning? If so, clean the EGR valve and throttle body elbow then reset the computer and wait to see if a code is trown again.

Good luck.

 

Good Info Guys, in response

HOSE FITS

1. Checked Hoses, The new DPFE sensor has a large and a Small Port, The hoses match and they match the EGR tube. One suspect issue is maybe a crack in the hose, I did not replace hoses and the ends are a little brittle.

2. One Item - When I installed the EGR tube, (new) the fit to the shorty headers was a bear to get in, I may have the flange ****ed at an angle at the headers - maybe I have a leak ? Thoughts on this.

3. Just took the truck for a 1000 mile turkey hunt, and the code appeared four times, three times directly after a full tank and getting on the highway in the first 10 miles.

ELBOW CLOG

1. When I installed the new engine - one port was clogged but I cleared it and cleaned the part very well.