Hi guys, I'm new to the forum and this is my first post. I've searched a few of the ford truck sites and lots of people had issues with a 1401 and 1408 and there is an entire laundry list of things to check. Does anyone else know if I only have the 1408 is there there a shorter list or even an exact thing i should check first? I would prefer not to just start buying and replacing parts if it's not nessesary.

A little history if it helps. When I first bought the truck the light cam on, I brought it back to the dealer and they told me the cleaned the vacuum tubes, the light went off.... for about a week. Then I took it to a friend and he found a couple of the tubes loose, tightened them and the light stayed off for about a year. Recently I performed surgery on the thing (sparkplugs may as well be on this model, haha) and after putting everything back together the tubes came loose again with a light and once again the light went off for a couple weeks. Now it seems as though all the tubes are tight but the p1408 code is still there. While the tubes were loose is it possible that dust or something was sucked into the system and that is whats causing the issue? Is there a filter or screen somewhere that could be clogged? Thanks ahead of time for any help.

2000 F150
5.4L XLT 4x4 Supercrew
~108,000 miles

 

1408 failure code is the same 'type' of test failure as a 401 except when the test is called to run, being the only difference and tells some info to a tech looking at it.
Basicly the EGR is commanded to open a programmed amount for expected flow.
The DPFE measures this flow across a restriction in the pipe leading to the EGR as a way to tell if there are problems.
The DPFE has small hoses attaching to the main pipes stand tubes.
These hoses must be "non-leaking" at any point. If you have problems here, get new hoses or put clamps on them.
As for possible reasons the fault exist, it could be the hoses, the DPFE, the EGR valve or it's port to the intake is carboned up, the vacuum hose to the EVR or to the EGR.
This test usually has to fail two times in a row to set a code and a lamp.
If it clears by it'self, it would have to pass two times during drive cycles to put the lamp out and clear the code.
You have intermittant failure that needs to be found. Nothing in between , about or any guessing will do.
Tighten any hose connections and inspect the metal tubes for cracks, rustout holes etc.
For testing; apply vacuum to the EGR while the engine is running. The engine should get rough and or stall out indicating the EGR is able to open and the paths thru to the intake is open.
At the DPFE tubes, you should be able to feel sleight exhaust pulses coming out of each tube while the engine is at idle as indication the restriction is open in the main tube.
Otherwise if no problem indications and the small hoses fit tight, the DPFE is suspect.
This is a designed system in both hardware and software so nothing is simple as you would like it to be so some understanding is in order to know what you should see or get help from a dealer that will fix it correctly.
Further, there are other tests done about the EGR system that picks up faults in other specific areas. Since no other codes are set, the aformentioned should be focused on.
The 1401/401 test is very tight on limits and makes the faults very sensitive to detection. This is why there are so many that have this fault code so often to the exclusion of many others..
The DPFE is only a test sensor and is subject to being detected as a fault by it'self as part of the total result.
Good luck.