I'm finally throwing up my hands and turning to the forum for some neighborhood help.

Background: 2003 Excursion and PCM with a 2005 6.0L. Bought (unknown to me at the time) with egr delete, no cat, frozen turbo, bad injectors, blown head gaskets, bad engine fan, bad water pump, clogged oil/water cooler, making oil, and the list goes on and on. Originally had a P0299 and P0401 code but others popped up along the way.

Work done: BPD EGR cooler, BPD FICM, BPD oil/air cooler, coolant filter, coolant flush (restore and restore plus) with ELC coolant, Garrett stage II turbo with wicked wheel, 8 injectors, new heads and gaskets, ARP studs, silicone turbo boots, water pump, fan, thermostat, radiator cap, blue spring upgrade, new fuel filters, 08' transmission pan/filter upgrade, transmission dummy plugs, fuel tank pickup foot, all new rubber hoses, STC upgrade, Dummy plug upgrade, Map sensor, Baro sensor and direct wire (harness issue), repined and repaired over a dozen harness plugs including; glow plug harness', FICM harness', PCM connectors.

After the BPD EGR replacement, the codes cleared (miraculously) long enough to smog. Since then, all the other work has been done with a variety of codes popping up, only to be replaced by a new one. So currently, I am back to getting a P0401 code that will come back a day or two after clearing the code. EGR monitor will not set.

I am at a loss. I have put so much into this thing over 3 1/2 years and still cannot get it smogged. I took it to the last shop for a baro code that would not go away. No other code issues at that time. They had it for 6 months and when I got it back, the EGR monitor, P0401, and injector codes have been the new problem. They had me pay for a new PCM, then put my old one back in with a reflash because the new PCM didn't fix the baro problem. They bypassed the wiring harness and direct wired it to the PCM which fixed the baro code. When I got it back I did the 8 injectors because I was still making oil and had #1 and #3 injector codes. I then upgraded the turbo, wheel and boots. I have SCT livewire and AE to monitor. Iv'e read for hours on people trying to fix the P0401 and most surround the EGR cooler but that has been done. My brain is just not seeing a new aspect of this problem so turning to FTE for a fresh set of eyes. My MAF sensor has a small crack in the top of the sensor and the engine side of the intake has a warp to it probably letting some post filter air in. Thanks.

 

The intake manifold has a torque sequence and it you don't do it that way you will have a sealing issue.
Have you removed the IA2 sensor and cleaned it with brake clean? IF the sensor is bad or not making
good contact you could also get P0401 DTC. With the fact that you have a CALF truck it might be that
the programing is looking for the change in the IA2 sensor when the EGR valve should be opening.
With an EGR delete you will not get the increase in intake temp like you should and the code will set.

Is the EGR removed or welded? I hate to tell you to put a good EGR cooler into it but I think that might
be the fix for the P0401. If you find that is the route your going to take then you can also fix the intake
​​​​​​​at the same time.

 

Nice post Sean.

OP - you might also try cleaning the IAT2 sensor .... and make sure that the MAP sensor nipple on the manifold is not plugged

 

Thanks for the catch on that. I thought I had posted that.

 

I already changed the EGR cooler to the BPD cooler. I have been religious about torques and sequences since I've taken this down to the block and did head gaskets as well. I'll check them again. That's one thing I've read, that even the slightest air leak anywhere from the MAF to the cat can cause this code.

Map hose is clear and it's a new sensor also.

I'll try cleaning the IA2 sensor, but is brake cleaner safe? I've read specifically not to use break cleaner on air temp sensors. When I monitor IA1 and IA2, IA2 changes with EGR change.

 

I use an electronics cleaner

https://www.napaonline.com/en/p/CRC0...BoCBhMQAvD_BwE

Or MAF cleaner
https://www.napaonline.com/en/p/CRC0...ut=maf+cleaner

 

I have used brake clean on the IA2 but NOT on IA1as it's part of the MAF.
MAF cleaner should also work very well to clean that sensor. Just don't use a brush.
The little red straw you put on the spray can should work quite well to help remove the
gummy good from the sensor.

The reason I asked about the torque steps is I almost goofed on the first one I did and
what I was shown when not using the one side then the other step was a gaping separation
between the head and the manifold..

 

You replaced the EGR cooler with one from BPD, but did you test the EGR valve itself?
With KOEO, Check the EGR valve position (EGRVP) - it should read between 0.4 - 1.2 volts
If your scan tool will let you, command the EGR valve position desired (EGRVPDES) to 100%
Voltage on EGRVP should now read 3.3 - 4.7 volts
If difference between the values isn't at least 2.71 volts, PCM will throw the code.
Might indicate a bad EGR actuator.

 

I change the EGR cooler three and a half years ago. I just checked the EGR valve at koeo and get 0.66 volts. I checked it at 90% and get 3.51 volts. I can watch the plunger actuate. I also get an IA1 and IA2 differential when driving. Cleaned it and put it back.

 

Update. Checked IA2, cleaned it, compared cold temp against IA1, added heat and it responded properly. MAP tube and intake clear. Intake bolts all torques property. There are three things I'm not sure if they contribute; crankcase vent tube was missing green o-ring. Also, the back part of the air filter is warped so it lets some post filter air in. Lastly, the top of the MAF sensor hada crack in the plastic.

 

My 2005 doesn’t use the MAF sensor. Has the plug but no sensor. Does the programming in your PCM require the MAF? Unplug the sensor and see what happens

 

It does as far as I have read and studied. Even though the engine is an 05' it still uses the 03' PCM. If I remember right, it even ties into the engine fan control. Additionally, the MAF includes the IA1 sensor, which is used to correlate temp changes with EGR flow.

 

Ok wasn’t sure it still had the 03 PCM

 

Are there any smog individuals in here? Will I be able to pass smog with a P0401? The problem I had before was the EGR monitor would not set even with hours and hundreds of miles of driving. Yesterday the EGR monitor finally set. I do not have any check engine light, it's just the soft code P0401.

 

This is an issue they would fail the truck on.
OBD II code P0401 Exhaust EGR Flow Insufficient. The OBDII fault code P0401 means that the engine computer
has detected that the Exhaust Gas Recirculation (EGR) system flow is insufficient. The EGR system redirects a small
amount of exhaust gases back into the intake.

Have you tried to clear the DTCs as this might be just an old code?
The problem with clearing is you will loose the redness status.
If this is just an old code waiting to clear it will go away with some drive cycles.