Need Some P0405 EGR Halp, STAT!

[dlyoung1]

Morning, folks! I seriously need some advice on my wife's '03 XLT 4.6L. I have a recurring (off and on for the last year) P0405 code for "EGR Sensor A Circuit Low" and now, new just this morning I have P0403 "EGR A Control Circuit". MUST get these corrected for state inspection here in Texas.

Bear with me for some background on what I've done so far and why I'm confused. Went to "The Shadetree Mechanic's Best Friend" (YouTube) and got some troubleshooting advice.

1.) Took the vac line off of the EGR valve itself and replaced it with a good vac source upstream of the DPFE module. Immediately started idling very rough, though not quite to stall. That should tell me the valve is opening as it should (though perhaps not fully?).
2.) Took the throttle body apart and thoroughly cleaned a bunch of carbon out of both of the EGR passages, and I'm assuming I got it all.
3.) To test the control solenoid, I removed the wiring harness connector and jumped power to the input, the solenoid engaged and the valve opened to produce the same rough idle. At this point, I'm thinking solenoid works when it gets a control demand and EGR valve opens like it should.
4.) Replaced the DPFE module to no effect at all.

This is where I'm stumped. I think I have individually looked at all of the components in the chain and they all seem to check out, plus cleaning the throttle body passages. From most information sources I have seen, if there was a "computer" glitch I would probably be getting all kinds of malfunctions across multiple subsystems.

Then there is the brand new Control Circuit code this morning that I haven't even looked into yet. Who can give me a point in the next diagnostic direction? Any input would be GREATLY appreciated! Thanks.

 

[Hamfisted]

Did you pull the EGR off and check that it's valve is closing all the way ? (free of carbon buildup...). Could be EGR valve is stuck partially open. Not enough to really rough up the idle, but enough to throw a code. If it's carboned up you can clean it, or replace it, whatever you find works best.

https://www.rockauto.com/en/catalog...+v8,1411108,exhaust+&+emission,egr+valve,4968

 

[dlyoung1]

For whatever dumb reason, that's pretty much the only thing I haven't done. Let me pull it and do a thorough cleaning. Thanks for the input.

 

[RichardH]

I had some gremlin EGR code, pointed at the DPFE, (that's the EGR pressure sensor, right?).

So I installed (or my mechanic on valve): new pressure sensor, 2 hoses that go to the pressure sensor, EGR valve. Still got code. So point is even if new part, still could be causing code...

Unfortunately turned to dealer (stupid money/cost) to get rid of the CEL. Turns out the pressure sensor I bought off of Amazon was faulty. They replaced with Ford part and all is well. Unfortunately I can't recall the code, but don't think it's your code.

 

[dlyoung1]

UPDATE - This dang thing is driving me crazy! Here is the latest: Took the valve itself off a few days ago and gave it an inspection and cleaning. Didn't have any noticeable carbon build-up in the valve body but gave it some carb cleaner anyway. Verified valve opening and closing fully by "borrowing" a vac source from my idling Jeep, so I feel the valve itself is good. Put it back together and cleared the code. Drove it locally for about three or four days before the P0401 "EGR A Flow Insufficient Detected" displayed.
Honestly, I'm getting tired of this whole thing. What are the chances of the sensor ports on the EGR tube getting clogged?

 

[98eb5.4]

https://www.fixmyoldride.com/EGR-codes-on-Ford-pickups.html
check The EGR Position Sensor or DPFE part

ended up here also

So I installed (or my mechanic on valve): new pressure sensor, 2 hoses that go to the pressure sensor, EGR valve. Still got code. So point is even if new part, still could be causing code...

Changing parts even with new can certainty end up hit or miss.

Bottom line is U can try easy cheap stuff first with plenty of info out there, then or if requiring a fast fix, find & pay someone who knows the system & can diagnose what the problem(s?) actually is.

There is a step by step diagnostic process to follow, can't find a/the good one that was around years ago, here's another
https://www.engine-codes.com/p0401_2003_ford_f150.html

My p0401 ended up being an easy (2 bolts & connections) dpfe sensor swap, after wasting a ton of time, effort & green...it was the first thing I changed out with a new part, that also ended up being bad..

I'd think a full complete diagnostic would be 1 to 2 hrs labor max, if even having to go that far, might get lucky & catch a known issue(s) quick..

Sounds like u've made some progress..
https://www.f150online.com/forums/v8-engines/156536-error-code-po401-2.html#post1315276

https://www.f150online.com/forums/v8-engines/156536-error-code-po401-2.html#post1315460

I ended up dealing with the usual, common blockage info bit, that i found to be a PIA job, tight spaces & having the right tools, including a fair amount of work etc.. only to find out it was all good at ~ 300k miles.

 

[Plati]

I had a different code & think you already checked this but wasn't sure so ...
https://www.expeditionforum.com/threads/p1405-egr-sensor-fault.37525/

^^^post that Mr98eb54 put up is awesome!